According to the ancient Hindu reli-gious texts like the Bhagavadgītā (3.10, 11) Prajāpati (the Creator) gave the yajña (system of sacrifices) as the link between the human beings and the deities (devas) of the cosmic regions. Human beings were advised to propitiate these deities through various yajñas and the deities in turn would respond by bestowing upon them their needs.
Vedic sacrifices which were simple fire rituals during the Saṁhitā period were gradually developed, by the period of the Brāhmaṇas, into a bewildering variety of rites and ceremonies with a labyrinth of details. One of the complicated sacrifices is the Somayāga of which agnicayana forms an integral part. However this rite is not compulsory even in Somayāga. Literally the word means ‘piling the fire’ but in practice it refers to the rite of building up the altar on which the sacrificial fire (āhavanīya) will be lighted.
The Śatapatha Brāhmaṇa (kāṇḍas 6 to 10) of the Śukla Yajurveda, which is the basic authority on this rite, represents it as a human imitation of the construction of the cosmic world of Prajāpati.
Detailed instructions are given for the manufacture of the various kinds of bricks, of different shapes and sizes, and for the building up of the altar in several layers and of prescribed shapes. The most common shapes are those of suparṇa (eagle), śyena (hawk) and droṇa (trough). As many as 10,800 bricks are needed to complete the construction of the altar. A thorough knowledge of geometry is necessary on the part of the priests who guide and direct the construction. The bricks are usually laid in five layers, the 1st, the 3rd and the 5th being of the same pattern while the 2nd and 4th are different.
Measuring the ground on which the altar is built, ploughing and sowing it with several seeds, interring the heads of five animals or their golden images and the golden image of the sacrificer as also a living tortoise into the altar that is being built are some of the details mentioned in the liturgical works.
The piling of the altar could be completed in one year (8 months for the first four layers and 4 months for the last) or only in five consecutive days.
The ‘Agnicit,’ i.e., the person who performs agnicayana, is expected to observe certain vows during this period. He is permitted to do ‘punaściti’ (doing agnicayana once again) if he does not prosper in the year after performing it.
To obviate the effects of the sins of omission and commission during the agnicayana rite, several prāyaścittas (expiations) are prescribed.
The esoteric doctrine of agnicayana is said to have originated with Prajāpati himself and come down through a succession of teachers from Tura Kāvaṣeya to Śāṇḍilya.