Vedic sacrifices were the most common aspects of practical religion in the early days of Hindu civilization. Among them, one variety called Somayāga is said to have seven ‘saṁsthās’ or forms. They are: Agniṣṭoma, Atyagniṣṭoma, Ukthya, Ṣoḍaśin, Vājapeya, Atirātra and Aptoryāma.
Atirātra, the sixth in this series, derives its name from the fact that its performance extends beyond a day and a night. It is said to be a modification of Agniṣṭoma. Since it is mentioned in the Ṛgveda (7.103.7) it can be inferred as a very ancient sacrifice. The chanting of 29 stotras and 29 śastras, (the additional ones being recited in the night in four rounds), offering of six oblations in the night, chanting of the long Āśvinaśastra (comprising 1000 verses) at dawn, sacrificing an ewe to Sarasvatī on the day of pressing the soma juice, offering of puroḍāśa cakes in potsherds to the twin Aśvins—these are some of the essential features of this sacrifice.
(For details of the technical terms used here, see under the respective titles.)