Yantra Shastra (यन्त्रशास्त्रम्)

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Yantra (Samskrit: यन्त्रम्) refers to contrivances or instruments developed using the fundamental knowledge of mathematics, astronomy, physics, chemistry, agriculture etc., for enabling ease of activities in daily lives. On the other hand, in worship and ritualistic works they are regarded as devices for devotional sadhanas. These are used as tools for mental concentration and meditation. Enormous scientific marvels of modern day mechanical interventions and development of instruments and appliances in the past few centuries, may lead to a misplaced conclusion that sciences have only developed in the recent few centuries.

The discovery of ancient manuscripts and the advance of research have both brought to light no insignificant amount of ancient Indian activity in the fields of positive aspects of life, of subjects of practical interest and scientific value, which reveal a holistic intellectual advancement in Bharat bringing about outstanding contributions in the fields of ganita, jyotisha, ayurveda, agriculture. It is these earlier experiments that have been the forerunners of the recent advancements in the field of science and technology, many of which continue to exist as the foundational principles of modern day appliances and technical advancements.

परिचयः ॥ Introduction

As an appliance, yantras may be astronomical, surgical instruments, or a machine or mechanical device. In a traditional view, a yantra is a diagram containing geometrical drawing and includes symbols, mantras, letters, numbers and other figures (ex., Sriyantra, Sarvatobhadra yantra). In the context of ganita, anka yantras, called as magic squares have been used since the times of Varahamihira.

That from ancient times the idea of a yantra was very common is proved by two facts, the application of the concept to the esoteric sphere, and the way the yantra roused the imagination of the spiritual writers. In esoteric worship the yantra was a chart which stored up within its confines spiritual power; drawn on' a flat surface or made in relief, it had components or details which had to be strictly conformed to and, as an instrument for achieving spiritual power, it eminently deserved the name "yantra."

Some very simple yantras are commonly known: the water-pulley in the well was called Ghatiyantra ; an oil-presser was Taila-yantra (तैलयन्त्रम्); wooden contrivances for pounding rice was kuttakayantra (कुट्टकयन्त्रम्); a cane-presser was Ikshu-yantra; ploughs, water-lifts and even weighing balances were referred to as yantras (Arthashastra 2.19). Complex yantras were used in warfare, astronomy and vimanas (aerial cars).

Yantras, in Indian medicinal texts of Ayurveda, refer to instruments used in surgery (shalya chiktsa). Rasashastra texts of Ayurveda, mention the term Yantra to describe apparatuses used for preparation of Rasa drugs (rasa-aushadha-nirmana). The construction of yantras is described in the ancient literature with definite measurements and details for each arrangement. As per Rasasastra, metals and minerals needs to undergo specific procedures like shodhana, marana etc., before they could be administered into the body. All of this could be achieved with the help of yantras. Thus yantras have various meanings based on the context of usage as follows

1. mechanical contrivances (machine or instrument) eg., kupa yantra (for drawing water)
2. an engine or machine
3. astronomical instruments
4. mathematical measurement tools (sanku, anka-yantras or numerical diagrams)
5. geometrical designs used as tools for meditation (pujana yantras)
6. instruments used in ancient surgical procedures
7. contraptions or apparatuses used in Ayurvedic system of Rasashastra

व्युत्पत्तिः॥Etymology

Yantra is a term having quite a few etymological connections and explanations as apparent from various works.

• Apte gives the root यन्त्र् (yantr) that which restrains or fastens, any prop or support, a stay; A fetter, band, fastening, tie, thong, rein; A surgical instrument...
• Vachaspatyam and Dhatu Sagara taranih mention that yantra is connected to the root यत्रि (yatri) used in the sense 'to curb, to check.'
• Shabdakalpadhruma mentions the root as यम (yam) used in the similar sense as given in Vachaspatyam.
• The word yantra is derived from the dhatu यम् (yam) used in the sense "to control", and has been freely used in ancient India for any contrivance or machine. In Samarangana Sutradhara, Maharaja Bhojadeva defines Yantra as follows

यदृच्छया प्रवृत्तानि भूतानि स्वेन वर्त्मना। नियम्यास्मिन् नयति यत्तद्यन्त्रमिति कीर्तितम् ॥३ yadr̥cchayā pravr̥ttāni bhūtāni svēna vartmanā| niyamyāsmin nayati yattadyantramiti kīrtitam ||3 (Sama. Sutra. 31.3)

स्वरसेन प्रवृत्तानि भूतानि स्वमनीषया। कृतं यस्माद्यमयति तद्वा यन्त्रमिति स्मृतम् ॥४ svarasēna pravr̥ttāni bhūtāni svamanīṣayā| kr̥taṁ yasmādyamayati tadvā yantramiti smr̥tam ||4 (Sama. Sutra. 31.4)

Dr. V.R. Raghavan in his article “Yantras or Mechanical Contrivances in Ancient India” describes that yantra is so called because it controls and directs according to a plan, the motions of things that act each according to its own nature. Thus, Yantra usually means any appliance or apparatus, contrivance, or device, engine or machine, implement or instrument in general. Depending on the context, it may specifically denote an object of any or the above type in different areas of Indian Sciences in a broad sense.

• Ayurveda makes use of the word 'tantra' in the sense of 'body' and 'yantra' in the sense of its machinery. In traditional Rasayana shastra, different types of apparatus used in the processing of medicines (aushadhis) and mercury and other preparations (rasas) were called yantras. Rasatarangini mentions

  रसोपरसलोहाद्यः मारणद्यर्थसिद्धये । यन्त्र्यतेऽनेन यस्मात्तु तस्माद् यन्त्रं प्रकीर्तितम्॥ rasōparasalōhādyaḥ māraṇadyarthasiddhayē | yantryatē’nēna yasmāttu tasmād yantraṁ prakīrtitam|| (Rasa. Tara. 4.1)

  Yantras are apparatuses used for the shodhana, marana, swedana etc purposes of rasa, uparasa, lohadis.
• In Ganita-Jyotisha (mathematical astronomy) the astronomical instruments have been called as yantras.
• In Tantra shastra, Yantra is used to refer to a geometrical pattern, a synthesis of lines and 'beeja aksharas' or 'seed letters'. Tantra technically is a process of relating the unusual patterns (yantra) with uncommon formulae (mantra). Basic to both these patterns and formulae is the belief that the human body is the ground where they operate. Yantras are merely extensions or externalizations of the forces purported as working within the individual; and Mantras are in the nature of formalisations of the vibrations occurring within. A few largely used yantras mostly for protection, health and warding off evil include those such as Vishahara yantra for snake bite, Rogahara yantra for curing consumptive ailments, Svarnabhairava yantra used in Alchemy, Kartavirya yantra for recovering lost property etc.

However, the present article discusses the yantras as mechanical contrivances, instruments and apparatuses with an aim to bring out the scientific aspects in the field of mechanical and physical sciences, the knowledge of which shastras were well developed and widely used in fields such as Agriculture, Mathematics, Warfare, and Ayurveda.

Yantras in Ancient Literature

Vedas

Dr. Raghavan's research about yantras in Vedic literature are as the following

1. One of the best creations of the most ancient architects of this country is the chariot, Ratha. Rigveda, mentions about them as रथं न धीरः - Dhira and Manisin (Rig. Veda. 5.2.11; 5.29.15) The Rathakara of Vedic times was ever a gifted person of importance and was regarded to have high mental skill, according to the Vajasaneyi-Samhita the Sathapatha-Brahmana and the Atharva-veda.
2. The Ribhus, Visvakarman and Tvashtar of the Vedas and the anonymous Vedic Takshan are succeeded in the epics by the two great architects of the Devas and the Asuras, viz., Visvakarman and Maya.
3. The Vedas further mention the apparatus for producing fire namely, Aarani. The principle of churning action used to produce fire is applied for churning of milk.

Thus, wheel was an important yantra that found mention in early Vedic literature.

Ramayana

Interesting references are made by Valmlki to yantras on the field of battle, the continuity of which tradition we see later in the Arthashastra of Kautilya. In Valmiki Ramayana we see the use of yantras for warfare and protection.

कच्चित् सर्वाणि दुर्गाणि धन धान्य आयुध उदकैः | यन्त्रैः च परिपूर्णानि तथा शिल्पि धनुर्धरैः || २-१००-५३ (Rama. Ayod. Kand. 2.11.53)

While enquiring about measures of defence, Rama asks Bharata whether the forts are equipped with money, grains, weapons, water and yantras as well as shilpikars and archers.

Lanka, as a city built by Maya, is naturally more full of the yantras. The city, personified as a lady, has yantra-agara-stani, special chamber filled with yantras (as the breast) in Sundarakanda as follows

ताम् रत्न वसन उपेताम् कोष्ठ आगार अवतंसकाम् | यन्त्र अगार स्तनीम् ऋद्धाम् प्रमदाम् इव भूषिताम् || ५-३-१८ (Rama. Sund. Kand. 5.3.18)

Hanuman looked at the city of the demon king, whose darkness was dispelled by bright gems and mighty mansions as if it were a young maiden. The prosperous city was like a well decorated woman, adorned with ornaments having walls for her dress, the stables for her earrings, the armouries for her breasts.

In his account to Rama of the fortifications of Lanka, Hanuman in Yuddhakanda, describes that Lanka has four big gates and that each gate is furnished with strong and huge yantras that can hurl both arrows and stones (Upala-yantras):

तत्रेषूपयन्त्राणि बलवन्ति महान्ति च | आगतम् पर सैन्यम् तैस् तत्र प्रतिनिवार्यते || ६-३-१२ (Rama. Yudd. Kand. 6.3.12)

द्वारेषु तासाम् चत्वारः सम्क्रमाः परम आयताः | यन्त्रैर् उपेता बहुभिर् महद्भिर् दृढ संधिभिः || ६-३-१६ (Rama. Yudd. Kand. 6.3.16)

And over the moats are extensive draw-bridges which are controlled by numerous big yantras. Against the approach of the enemy forces there, the draw-bridges are protected by the aforesaid engines and the enemy-battalions are flung into the moats on every side. That such yantras were employed on the field is seen in a description of Kumbhakarna, where his giant figure striding the streets of Lanka is compared to a huge yantra that has been set up to kill the vanaras.

उच्यन्ताम् वानराः सर्वे यन्त्रमेतत्समुच्छ्रितम् | (Rama. Yudd. Kand. 6.61.33)

Thus there are many instances in Ramayana where yantras were greatly used in warfare and the technology was very advanced.

Mahabharata

In the Mahabharata we hear of the Matsya-yantra or the revolving wheel with a fish which Arjuna had to shoot in order to win Draupadi in the svayamvara. In the Harivamsa, a supplement to the Mahabharata, there is mention of the stone-throwing machine, Asma-yantra, in the battle with Jarasandha (II. 42. 21). The great architectural skills of Maya are vividly described the Intraprastha sabha of Yudhisthira.

Arthashastra

The Arthashastra of Kautilya is one of the books of culture which throw a flood of light on the particular time in which they arose. An ancient valuable treatise on statecraft, it speaks of yantras mainly in connection with battles, and with architecture to some extent.

The main yantras of warfare are discussed by Kautilya in the Ayudhagara adhyaya wholly devoted to armoury. However, other mechanical contrivances described by him pertain to construction of forts with restrictive secret passages, movable staircases, controlling animals like elephants, for protecting against unwanted intruders in many situations.

In II. 5 of Arthashastra, he refers to a dugout, Bhumigriha, and mentions for it a mechanical staircase which can be thrown in and withdrawn (Yantra-yukta-sopana). While detailing the exact methods to be adopted for finishing off enemies and unwanted persons (XII. 5), Kautilya speaks of machines which could be conveniently pressed into service. When the unwanted person is entering a temple, from an overhead yantra there could be released on his head a piece of masonry or a stone to kill him instantly.

It mentions a manually operated cooling device referred to as “Variyantra” (revolving water spray for cooling the air). The Variyantra was similar to the water cooler. According to Megasthenes (an ancient Greek historian, who visited the court of king Chandragupta Maurya around 300 BCE), the Variyantra was used by the wealthier sections of the society for cooling the air. The Arthashastra also gives an extensive account of hydraulic structures built for irrigation and other purposes during the period of the Mauryan Empire.

Mechanical Contrivances

Constituents the Elements of Yantra

According to Bhojadeva in his seminal work Samarangana Sutradhara, Bija or Constituent elements of yantra are four in number.

तस्य बीजं चतुर्धा स्यात् क्षितिरापोऽनलोऽनिलः। आश्रयत्वेन चैतेषां विजयदप्युपयुज्यते ॥५ (Sama. Sutr. 31.5)

They are earth (क्षितिः), water (आपः), fire (अनलः) and air (अनिलः) with ether (विजयः) being the medium of action.

Qualities of a good Yantra

According to Bhojadeva, the capability of the yantra cannot be decided just by looking at its shape. He describes the merits of good machine as follows.

यन्त्राणामाकृतिस्तेन निर्णेतुं नैव शक्यते। यथावद्बीजसंयोगः सौश्लिष्ट्यं श्लक्ष्णतापि च ॥४५

अलक्षाता निर्वहणं लघुत्वं शब्दहीनता। शब्दे साध्ये तदाधिक्यमशैथिल्यमगाढता ॥४६

वहनीषु समस्तासु सौश्लिष्ट्यं चास्खलद्गति। यथाभीष्टार्थकारित्वं लयतालानुगामिता ॥४७

इष्टकालेऽर्धदर्शित्वं पुनः सम्यक्त्वसंवृतिः। अनुल्बणत्वं ताद्रू प्यं दार्ढ्ये मसृणता तथा ॥४८

चिरकालसहत्वं च यन्त्रस्यैते गुणः स्मृताः। (Sama. Sutr. 31.45-49)

yantrāṇāmākṛtistena nirṇetuṃ naiva śakyate| yathāvadbījasaṃyogaḥ sauśliṣṭyaṃ ślakṣṇatāpi ca ||45

alakṣātā nirvahaṇaṃ laghutvaṃ śabdahīnatā| śabde sādhye tadādhikyamaśaithilyamagāḍhatā ||46

vahanīṣu samastāsu sauśliṣṭyaṃ cāskhaladgati| yathābhīṣṭārthakāritvaṃ layatālānugāmitā ||47

iṣṭakālē’rdhadarśitvaṁ punaḥ samyaktvasaṁvr̥tiḥ| anulbaṇatvaṁ tādrūpyaṁ dārḍhyēm asr̥ṇatā tathā ||48

cirakālasahatvaṃ ca yantrasyaite guṇaḥ smṛtāḥ|

1. yathāvadbījasaṃyogaḥ - Proper and proportionate utilization of constituent elements.
2. sauśliṣṭyaṃ - Well-knit construction
3. ślakṣṇatā - Firmness of appearance
4. alakṣātā - Inscrutability
5. nirvahaṇaṃ - Functional efficiency
6. laghutvaṃ - Lightness
7. śabdahīnatā - Freedom from noise
8. śabde sādhye tadādhikyam – A loud noise when noise is intended
9. aśaithilyam - Freedom from looseness
10. agāḍhatā - Freedom from stiffness
11. vahanīṣu samastāsu sauśliṣṭyaṃ - Smooth and unhampered motion
12. cāskhaladgati - Production of intended effects in cases where the ware is of curious category.
13. yathābhīṣṭārthakāritvaṃ layatālānugāmitā - The securing of the rhythmic quality in motion – particularly in entertainment wares.
14. iṣṭakālē’rdhadarśitvaṁ - Going into action when required.
15. punaḥ samyaktvasaṁvr̥tiḥ - Resumption of the still state when not required, chiefly in cases of pieces for pastime.
16. anulbaṇatvaṁ - Verisimilitude in the case of bodies intended to represent birds, animals.
17. tādrūpyaṁ - Firmness
18. dārḍhyē - Durability
19. asr̥ṇatā - Softness
20. cirakālasahatvaṃ - Enduring capacity for a sufficient period of time.

Classification of Yantras

According to different texts we find various versions of the classification of yantras. Bhojadeva in Samarangana Sutradhara classifies yantra mainly into three categories based on their characteristics. They are:

स्वयंवाहकमेकं स्यात्सकृत्प्रेर्यं तथापरम्। अन्यदन्तरितवाह्यं वाह्यमन्यत् त्वदूरतः ॥१० svayaṁvāhakamēkaṁ syātsakr̥tprēryaṁ tathāparam| anyadantaritavāhyaṁ vāhyamanyat tvadūrataḥ ||10 (Sama. Sutr. 31.10)

• स्वयंवाहकम् ॥ Svayamvahakam - That which is automatic and sakrt-prerakam (that which requires occasional propelling)

• अन्तरितवाह्यंम् ॥ Antarita vahyam - Where the principal of action or motor mechanism hidden or concealed from public view with the machine to be carried by another.

• दूरतःवाह्यम् ॥ Duruta vahyam - The one which is really obscure (distant proximate) but carriagable from the place from which the machine acts.

Kautilya in Arthashastra classifies yantras used in warfare as Sthira (unmovable) and Chala (movable) yantras both of which are discussed in the succeeding sections.

Bhattasvamin quotes a shloka on yantras in general as of three kinds, Vyadhita, Bhrdmita and Bharayukta: the first acts by being pressed, the second by rotation and the third by its sheer weight.

Samarangana Sutradhara by Bhojadeva is an eighty three chapter treatise which deals with town planning, house architecture, temple architecture, various sculptural subjects, canons of paintings, devotes a big chapter called Yantravidhanam (यन्त्रविधानम्) on the art of mechanical contrivances, the yantras. Chapter thirty one of this book specializes in mechanical contrivances and yantras, including those with construction of vimanas or aerial cars.

Yantras for Water-lifting

The Samaranganasutradhara (shlokas 110-14) describes four water-machines (vaariyantra) with fourfold movement in the vari-yantra or a fountain: (a) a downward flow from an overhead tank for which a Pata-yantra or waterfall-machine, is to be used; (b) Samanadika is for the release of water at a higher level from tanks placed at that level; (c) Patasamocchraya is a contrivance using bored columns for letting down water from a height, and then taking it up through columns placed aslant; and (d) the last, Ucchraya, in which water from a well or in a canal on the ground is sent up by a device. It is highly improbable that they were commonly used for irrigation.

The Kashyapiya-krshi-sukta (verses 167-69) gives an account of the devices for lifting water from a well and for using it for irrigating the fields. For raising water a place for fixing the machine is to be made on stone-slabs on the brink of the well, and for the outflow of water a small conduit is to be made on a hard surface near the edge of the well. Of the different kinds of machines for raising water the one drawn by bullocks yoked with strong chains is the best, that by the elephant with its trunk is the mediocre, and the one by human labour is the inferior-most. Water on lower levels in steadily raised to the surface of the wells etc. by the revolution of the water-raising machine. Water is then carried to the fields by means of small channels.

In Sanskrit the word Araghatta has been used in the ancient texts to describe the Persian Wheel. The ‘ara-ghatta’ comes from the combination of the words ‘ara’ meaning spoke and ‘ghatta’ meaning pot. There is evidence to argue that this system of lifting water from open wells was probably invented in India of the past. It finds mention in the Panchatantra (3rd Century BCE) and the Rajatarangini (12th century CE) as the ‘cakka-vattakka’ or the ‘ghati yantra’.

The waterlifting devices were also used in the Mesopotamian civilization, and the Saqia (or water wheel) was widely used for lift irrigation using oxen for irrigating the summer crops (Mays, 2008). The “asma-cakra” and “Ghatayantra” were widely in use during the Vedic and Mauryan periods. The Varshamaan was widely used in the Mauryan Empire for rainfall measurements. It may be noted that we do not have any reference to “rainfall measurement” in other contemporary civilizations in the Old World. Interestingly, the Rigveda (verses X, 93.12, and X, 101.7) has a mention of “asma-cakra” (a wheel made of stones). Water was raised with help of the wheel in a pail using a leather strap. There is also a mention of “Ghatayantra” or “Udghatana” (a drum-shaped wheel) around which a pair of endless ropes with ghata (i.e., earthen pots) tied at equal distances. The Arthashastra also mentions irrigating the agricultural fields by raising water from rivers, lakes, tanks, and wells using a mechanical device known as “Udghatam.”

Yantras for Warfare

Yantras for actual warfare are in general touched upon in several contexts : II.3 and 18 mention the need to equip forts with yantras. In X. 4, yantras on the field are said to be attended to by special labourers and workers. In IX.2, Kautilya deals with counter-maneuvers for tackling particular kinds of enemy forces; here, among the things to be used against elephants yantras or probably Hasti-yantras are included; these are machines in general or special machines designed to scare elephants; Bhoja, in his Samaranganasutradhdra, mentions that one of the uses of the aerial vehicle is to create a terrific noise and frighten elephants. In XIII.4, Kautilya advocates the use of yantras for devastating an enemy place which is full of defense-erections.

The chapter devoted wholly to armoury, Ayudhagara, book 2, adhyaya 18, is the main section speaking of military yantras. Kautilya divides the yantras into immovable and movable - Sthira and Chala yantras.

सर्वतोभद्र-जामदग्न्य-बहुमुख-विश्वासघाति-संघाटी-यानक-पर्जन्यक-बाहु-ऊर्ध्व-बाह्व्-अर्ध-बाहूनि स्थिर-यन्त्राणि ।। ०२.१८.०५ ।।

sarvatobhadra-jāmadagnya-bahumukha-viśvāsaghāti-saṃghāṭī-yānaka-parjanyaka-bāhu-ūrdhva-bāhv-ardha-bāhūni sthita-yantrāṇi || 02.18.05 || (Arth. 2.18.5)

Sthira Yantras

Sarvatobhadra : According to the commentary of Bhattasvamin, this is a sharp-edged wheel that is placed on a wall and rotated so as to fling big stones all around; according to others, it is also called Siddhabhumirika-yantra and scatters small stones.

Jamadagniya : Bhattasvamin explains it as a big Sara-yantra or mechanical arrow-thrower. It is placed behind a wall and it shoots arrows through crevices in the wall. But the name signifies a fire-arm.

Bahumukha : This is an elevation and a mount for archers; it is leather covered and is as high as the wall to enable archers to shoot all round.

Vishvasaghati : An iron bar placed across the path in the approaches to the city, which, manipulated by a mechanical device, falls down and pounds a man. It belongs to the class mentioned above for killing unwanted persons and the yantra-torana mentioned in the Mudrardkshasa.

Sanghati means "tied together". It was made of wood and used to set fire to enemy fortifications. It is called an Agni-yantra.

Yanaka or Yanika is a yantra moved on wheels; it discharges batons.

Parjanyaka is an Udaka-yantra, a fire-quencher.

Bahus are two arm-like pillars which when released from either side by a yantra, press to death a person between them ; this appears to be an instrument of torture. Urdhvabahu is similarly an overhead column which comes down upon a man and puts him to death. Ardhabahu is the same as Bahu, but is of dimunitive size.

पाञ्चालिक-देवदण्ड-सूकरिका-मुसल-यष्टि-हस्तिवारक-तालवृन्त-मुद्गर-गदा-स्पृक्तला-कुद्दाल-आस्फाटिम-उत्पाटिम-उद्घाटिम-शतघ्नि-त्रिशूल-चक्राणि चल-यन्त्राणि ।। ०२.१८.०६ ।। pāñcālika-dēvadaṇḍa-sūkarikā-musala-yaṣṭi-hastivāraka-tālavr̥nta-mudgara-gadā-spr̥ktalā-kuddāla-āsphāṭima-utpāṭima-udghāṭima-śataghni-triśūla-cakrāṇi cala-yantrāṇi || 02.18.06 || (Arth. 2.18.5)

Chala Yantras

Pánchálika - Its use is outside the fort walls, in the moat; thrown in the midst of the water, its sharp protruding points prevent the progress of enemies.

Devadanda are long cylindrical cannon-like things placed on parapet walls. Bhattasvamin gives them another name Pratitaroca.

súkarika is a huge thing shaped like a pig or bellows, made of bamboo, rope and hide, filled inside with cotton etc., and is placed on the path as an obstruction and as a buffer to stop stones, etc.,. that are flung by the enemy. According to some others, Sukarikas are to prevent enemies from easily getting up the ramparts; they, apparently, were probably closely suspended all along the walls to prevent the enemy-scaler from getting a foothold.

Musala and Yashti are well-known; hastiváraka is interpreted as a two or three-pronged iron rod, Hastiparigha, for striking at elephants, but may really mean, as seen from a reference in Dandin's Avantisundari, a machine which hurls heavy iron rods to smite and demoralize the elephants.

A tálavrinta is explained as a Vatachakra, the significance of which is obscure. It was a device to create a tempest which could demoralize the enemy ranks. The observation of Philostratus, relating to Alexander's invasion of India, that Indians drive the enemy off by means of tempest and thunders, as if from heaven, may, however, be only an echo of the Vayavyastra described in Ramayana.

After Mudgara, Gada, Sphriktala, a picked missile, and kuddála, are mentioned. ásphátima has four feet, is covered by hide, has a projectile and throws stones. udhghátima is a machine which demolishes, walls with the iron bars fitted to it, it is interpreted as the Syena-yantra which uproots and tears up things. The trisúla and chakra, are the well-known trident and discus. Sataghni, the centicide, is mentioned in all descriptions of warfare in old literature, but as to, the exact nature of which there is difference of opinion. Bhattasvamin takes it as a huge, cannon-like, cylindrical thing with wheels, placed on the parapet.

Ratha or Chariot

Ratha or chariot was an important piece of military equipment mentioned from the Vedic texts. It generally had two wheels (chakra), each having a rim (nemi), felly (pradhi), nave (nabhya) and spokes (ara), connected by a non-revolving axle (aksha), the end of which (aani) fit into the nave holes (kha). Solid wheels were also used. The Sulbasutra of Apastamba gives the dimensions to construct a chariot.

Yantras in Engineering

Ancient Indians were incredibly skilled in civil engineering, showcasing their prowess through remarkable feats of architecture and urban planning.

1. City planning - As seen from Mohenjodaro and Harappan excavations, there were advanced extensive water drainage systems, well laid out planned streets, and urban facilities. They were regarded as the world's pioneers in engineering and city construction as shown by their use of building materials, and construction of roads, drains etc. Arterial streets, road alignments, well-built houses with bricks having more than one floor, provision of sanitary amenities in houses, paved baths, underground sewer pipes are all indicative of the civil engineering skills of the people. Advanced community living is portrayed by two remarkable structures, viz., the Great Bath situated in the citadel mound at Mohenjo-daro and the Great Granary at Harappa.
2. Hydraulic structures - Advanced water supply and drainage system was the hallmark of the Harappan civilization's Great Bath. Use of vertical and underground sewer pipes, pulley wheels for drawing water from the wells, swimming pools, and use of paved baths and public drainage system is well evidenced in Harappan city. The step tanks in various cities of India such as Hampi in Karnataka, Gujarat and Rajasthan served as vital water sources and communal gathering spaces, harnessing the groundwater resources. The advanced knowledge of hydraulic engineering enabled them to harness the power of water for agricultural and domestic purposes. The importance of the hydraulic structures in the Mauryan period can be judged on the basis of the punishments or fines imposed on the offenders. As mentioned in the Arthashastra, “when a person breaks the dam of a tank full of water, he shall be drowned in the very tank; of a tank without water, he shall be punished with the highest amercement; and of a tank which is in ruins owing to neglect, he shall be punished with the middle-most amercement”.
3. Road network - The construction of extensive road networks facilitated trade and communication across ancient India. Notable examples include the Grand Trunk Road, commissioned during the Mauryan Empire, which connected major cities and regions, promoting economic prosperity and cultural exchange.
4. Architectural Innovations such as the rock-cut cave temples of Ajanta and Ellora, the towering temples of Khajuraho and Hampi, and the intricately carved stupas of Sanchi, are a testament to the unparalleled craftsmanship and knowledge of the ancient artisans. The Buddhist Stupas and Viharas depicted their engineering skills. Temple architecture stands testimony for the mathematical and constructional abilities of the ancient artisans.

Akasa-yantras

In Brihatkatha, the context where the description of the 'yantra' occurs is the longing of the pregnant Vasavadatta; in the Kashmirian version of Somadeva there is only a line saying that her dohada (longing) was fulfilled by manifold contrivances, yantras, etc., arranged by the Minister Yaugandharayana. But in Budhasvamin's version, Vasavadatta yearned to see the whole world from above in an aerial vehicle (Sloka 190); Rumanvan, the commander-in-chief, at once ordered carpenters to manufacture a flying yantra (sloka 196). The carpenters say that they know only four kinds of yantras, made respectively with water, stone, mud and twigs; that it is the Yavanas who know the Akasa-yantras, and that they, for their part, have not even laid eyes on them.

Vymanika Shastra

It is said that Maharishi Bharadwaja has written a book called “Yantra Sarvasva”. In that book, Chapter 40 titled “Vymanika Shastra or Science of Aeronautics” describes the design, construction and applications of various aircrafts. This book gives the clear classification of vimanas and explains in detail about the design and the materials used in the construction of vimanas. In the year 1952, G.R.Josyer discovered the ancient manuscript of this text written by Pandit Subbaraya Shastry. In the year 1959 Hindi translation of the text was first published, and thenpeople started knowing that such an amazing technology existed during our ancient era. Critics have alluded to various findings about the authenticity of the ancient texts and its origin mentioned above. However, Samarangana sutradhara of Bhojadeva which mentions the use of aircraft in ancient era lends support to the theories of vaimanika shastra.

Yantras in Pleasure and Entertainment

The yantras under this heading include accessories of pleasure and entertainment, and more properly under household fittings and architectural engineering. They include

• those yantras for reduction of human labour (fans, water showers, cool water sprays etc)
• parks, tree and fountains
• for sport and merriment
• toys and gadgets of miscellaneous kinds for entertainment

In Somadeva Suri's, Yashastilaka Campu, written in South India in 949 A.D., the first part of the work, describes the hero resorting to the cool yantra-dhara-griha to spend the hot hours of the summer days. This park, fitted with mechanical fountains, is appropriately called by the commentator Kritrima-megha-mandira, the artificial cloud-pavilion. It is erected in the dense garden in an area provided with many canals. There is the stream for water sports in the midst of which is a sandbank raised like a pavilion, provided with a water-bed, Salilaika tulika; nearby are numerous vessels containing fragrant water, at one end there is an yantra-jala-dhara, a contrivance producing artificial waterfall; the water is taken through and thrown out of the mouth's of figures of elephants, tigers, lions, snakes etc. Many artificial works adorned the palaces of kings, such as celestial damsels giving shower-baths, figures of monkeys spouting water, statuettes of water- damsels, (jaladevatas); there are wind-damsels (pavana-Kanyakas), wafting breezes with fly-whisks; and figures of ladies, scattering cool sandal-water all around. Somadeva Suri says of such a figure that if her hands were touched, she would emit sprays through her nails; if her face, through the eyes and so on. Somadeva describes how near the bed was a yantra-putrika, a mechanical breeze-lady was plying a fan for the King’s relief.

There is a corroborative evidence of such works from Bhojadeva's treatise and was not merely imaginative fictions. Mechanical fountains were constructed as necessary adjuncts to all palaces is seen in casual descriptions of many dramas. In Kalidasa's Malavikagnimitra drama, fountains or jala-yantras are mentioned.

बिन्दूत्क्षेपात्पिपासुः परिपतति शिखी भ्रान्तिमद्वारियन्त्रं bindūtkṣēpātpipāsuḥ paripatati śikhī bhrāntimadvāriyantraṁ (Malavikagnimitram. 2.12)

Contraption and Instruments in Ayurveda

Yantra in Ayurveda refer to surgical instruments on one hand and apparatuses or devices used to carry out various remedial processes on minerals and metals (or rasas) in a special branch of pharmacology in Ayurveda, termed as Rasashastra. Alchemical treatises of ancient India refer to various types of 'Yantras' or contraptions for different applications such as shodhana, jarana, marana, swedana etc. Yantras are commonly employed in the pharmaceutical preparation of rasoushadhis before they could be administered into the body.

Surgical Instruments

Yantras are blunt instruments used in surgical procedures and the removal of foreign substances lodged in different parts of the body. Nowadays, it is also used in diagnosing diseases. There are 101 types, according to Acharya Sushruta, which have been subdivided into five subcategories.

Classification of Yantras according to Acharya Sushruta

Yantras	Number	Size	Uses
Swastika yantras	24	18 angula	Asthi vidha salyodharana
Samdamsa yantra	01	16 angula	Twak mamsa sira snayu gata salyodharana
Tala yantra	01	12 angula	Karna, nasa, nadi salya aharana
Nadi yantra	20	as per need	Srotogatasalyoddharana, roga darsana, acusana, kriyasaukumarya
Salaka yantra	28	as per need	Esana, vyuhana, calana, aaharana
Upa yantra	25	as per need	Sarva deha anga, sandhi, koshta as and when needed

Contraptions

Rasasastra deals with metallic, mineral and poisonous drugs. These drugs are pharmaceutically processed and rendered fit for internal administration. For the various processing of rasa uparasadi dhatus and for the preparation of medicines, specific apparatuses called ‘Yantras’ are needed. Metals and minerals are required to undergo certain processes like shodhana, jarana, marana, satwapatana etc before they could be administered into the body and all these processes could only be achieved with the help of yantras. In Rasasastra, ashta samskara of parade is reckoned of great importance in enhancing the potency of parada both from the therapeutical and alchemical point of view. Specific yantras are needed for each of these processes.