Pranavidya (Samskrit : प्राणविद्या) is a special kind of upasana of Prana, the life force in this context, described in Aitareya Aranyaka. Aranyakas form a part of the Shruti texts available at the end of the Brahmanas of a particular veda samhita. Aitareya Aranyaka, consisting of five Aranyakas, is a part of the Aitareya Brahmana belonging to the Rigveda. The importance of Pranavidya is the special emphasis of Aranyakas. The quiet environment and solitude of the forests are the most apt locations to meditate on Pranavidya. Aitareya Aranyaka gives an exceptional account of this vidya (Aite. Aran. 1.1-3).
Aranyakas contain many descriptions of the yajnas as seen in the Brahmanas. These are texts which contain some hidden meanings about the vedic words are to be read by the people in vanaprastha ashrama, rishis and are not suitable for pregnant women, children. They have symbolic references of yajnas and detail the methods for Upasana. The references of Rig Veda mantras add strength to the concept of Pranavidya. Prana is said to be supreme among all indriyas as given in the second adhyaya of this Aranyaka (2.1.4).
सर्वं हीदं प्राणेनाऽऽवृतम्, इति । सोऽयमाकाशः प्राणेन बृहत्या विष्टब्धस्तद्यथाऽयमाकाशः प्राणेन बृहत्या विष्टब्ध । एवं सर्वाणि भूतानि आपिपीलिकाभ्यः प्राणेन बृहत्या विष्टब्धानीत्येवं विद्यात्, इति ।। (Aitr. Aran. 2.1.6)
sarvaṁ hīdaṁ prāṇēnāvr̥tam, iti । sō'yamākāśaḥ prāṇēna br̥hatyā viṣṭabdhastadyathāyamākāśaḥ prāṇēna br̥hatyā viṣṭabdha । ēvaṁ sarvāṇi bhūtāni āpipīlikābhyaḥ prāṇēna br̥hatyā viṣṭabdhānītyēvaṁ vidyāt, iti ।।
Summary : Every thing in this jagat is filled with or covered by Prana. Prana bears everything in the universe. By the power of Pranashakti, akasha is in its place. So also all the beings from the largest to the smallest ant are firmly supported by Prana.
Prana is Ayushkaraka
Without Prana the universe that we see in front of our eyes does not sustain, so Prana is all-pervading, omnipresent and protector. Hence in mantras Prana is called Gopa (गोपा). It is the reason for Ayu (आयुः । longevity). As long as Prana is in the shareera (body) till then life sustains. Kaushitaki Upanishad mentions the Ayukaraka nature of Prana as follows
आयुः प्राणः प्राणो वा आयुः प्राण एवाचामृतम् । यावद्ध्यस्मिञ्छरीरे प्राणो वसति तावदायुः । (Kaus.Upan.3.2)
āyuḥ prāṇaḥ prāṇō vā āyuḥ prāṇa ēvācāmr̥tam । yāvaddhyasmiñcharīrē prāṇō vasati tāvadāyuḥ ।
It was through Prana, that Antariksha ( loosely called as Space or Ether) and Vayu (Air) were created. A symbolic concept of Prana is that of the father and the sons as Antariksha and Vayu, who always serve the father. All beings with Prana are able to move in this Antariksha and it is the medium through which sound travels, thus Antariksha is subservient to Prana. The vayu brings sweets smells to the nose (indriya for smell) and satisfies the Prana inside the body as given by Aitareya Aranyaka below
प्राणेन सृष्टावन्तरिक्षं च वायुश्च । अन्तरिक्षं वा अनुचरन्ति अन्तरिक्षमनुशृण्वन्ति । वायुरस्मै पुण्यं गन्धमावहति । एवमेतौ प्राणं पितरं परिचरतोऽन्तरिक्षं च वायुश्च । (Aitr. Aran. 2.1.7)
prāṇēna sr̥ṣṭāvantarikṣaṁ ca vāyuśca । antarikṣaṁ vā anucaranti antarikṣamanuśr̥ṇvanti । vāyurasmai puṇyaṁ gandhamāvahati । ēvamētau prāṇaṁ pitaraṁ paricaratō'ntarikṣaṁ ca vāyuśca ।
Different forms and qualities of prana have been extensively described for upasana and meditation purposes.
Prana is Kalatmaka
In the form of day and night (अहोरात्रः), prana is described as a form of Kala or Time. Day is said to be Prana (प्राणः), while Night is called Apana (अपानः). In the morning Prana diffuses evenly in the body (प्रतनन) into all Indriyas or senses, called Pratayi (प्रातायि) which means one in whom there is a intense spread of Prana. Hence in the beginning of the day when one can visualise the effulgence of Prana, that time is called प्रातः। Prathaha (morning). At the end of the day when Prana is withdrawn into the Indriyas, called as Samaagat (समागात्), that time is called as सायम् । Sayam (evening). Due to progression or spread of Prana, Day is called Prana, while because of withdrawl, Night is called Apana.(Page 248 of reference)
तं देवाः प्राणयन्त स प्रणीतः प्रातायत प्रातायीतीँ३ तत्प्रातरभवत्समागादितीँ२ तत्सायमभवदहरेव प्राणो रात्रिरपानः, इति ।
taṁ dēvāḥ prāṇayanta sa praṇītaḥ prātāyata prātāyītīm̐3 tatprātarabhavatsamāgāditīm̐2 tatsāyamabhavadaharēva prāṇō rātrirapānaḥ, iti । (Aitr. Aran. 2.1.5)
Prana is Devatmaka
Prana is described as Devatas. In vak (वाक्) resides Agni (अग्निः), in eyes Surya (सूर्यः), in manas Chandra (चन्द्रः) and in the ears reside the Dishas (दिशाः। direction). In this step, one has to meditate upon all these devatas as residing in prana. A rishi named Hiranyadanvaida (हिरण्यदन्वैदः) reaped great benefits from performing such upasana.
वागग्निश्चक्षुरसावादित्यश्चन्द्रमा मनो दिशः श्रोत्रं स एष प्रहितां संयोगोऽध्यात्ममिमा देवता अद उ आविरधिदैवतमित्येतत्तदुक्तं भवति, इति । (Aitr. Aran. 2.1.5)
vāgagniścakṣurasāvādityaścandramā manō diśaḥ śrōtraṁ sa ēṣa prahitāṁ saṁyōgō'dhyātmamimā dēvatā ada u āviradhidaivatamityētattaduktaṁ bhavati, iti ।
Prana is Rishi-rupa
This is an exceptional concept wherein Prana is described as all the Rrshis and mantra-drastas. One has to meditate upon rishis as they are the very form of Prana.
Prana at the time of sleep, hides the speech, power of seeing etc i.e., covers all the indriyas such that they do not express themselves, hence Prana is called 'Grtsa'. At the time of conjugation, Apana forms the 'Mada' arising due to discharge of virya (seminal fluid), hence it can be said that union of Prana and Apana is 'Grthsamada'.