Changes

* 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.<ref>Prof. S. K. Ramachandra Rao. (1979) ''Tantra Mantra Yantra, The Tantra Psychology.'' New Delhi: Arnold Heinemann</ref>

* 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.<ref>Prof. S. K. Ramachandra Rao. (1979) ''Tantra Mantra Yantra, The Tantra Psychology.'' New Delhi: Arnold Heinemann</ref>

However, the present article pertains to 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.  

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 ==

== Yantras in Ancient Literature ==

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.   

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, 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.  

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.<ref name=":6">Pushpendra, K. S. Pankaj, Dey. Sharad, K. Jain. and Pradeep Majumdar. ''[https://hess.copernicus.org/articles/24/4691/2020/ Hydrology and water resources management in ancient India.]'' Hydrol. Earth Syst. Sci., 24, 4691–4707, 2020 <nowiki>https://doi.org/10.5194/hess-24-4691-2020</nowiki></ref>  

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.<ref name=":6">Pushpendra, K. S. Pankaj, Dey. Sharad, K. Jain. and Pradeep Majumdar. ''[https://hess.copernicus.org/articles/24/4691/2020/ Hydrology and water resources management in ancient India.]'' Hydrol. Earth Syst. Sci., 24, 4691–4707, 2020 <nowiki>https://doi.org/10.5194/hess-24-4691-2020</nowiki></ref>  

=== Akasa-yantras ===

=== 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.<ref name=":1" />

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.<ref name=":1" />

== Yantras in Pleasure and Entertainment ==

== Yantras in Pleasure and Entertainment ==