YV 2.7j

He who desires, 'May I be propagated', should sacrifice with (the rite) of twelve nights; verily he is propagated. The theologians say, 'The sacrifices have Agnistomas at the beginning; why then is Atiratra first employed?' The two Atiratras are the eyes of the sacrifice, the two Agnistomas the pupils; if [1] they were to employ the Agnistoma first, they would put the pupils outside; therefore the Atiratra is employed first; verily having inserted the eyes of the sacrifice they put the pupils in them. He, who knows the Gayatri to have sides of light, goes to the world of heaven with light and radiance. The sides are the Agnistomas, the eight Ukthyas in between are the body; verily the Gayatri has sides of light. He who knows thus goes to the world of heaven with light and radiance [2]. The twelve nights' (rite) is Prajapati in twelve divisions. The two sides are the Atiratras, the eight Ukthyas within are the body; Prajapati in such guise touches truth with the Sattra, truth is the breaths; verily he touches the breaths. Those who perform the Sattra perform it with the breath of all people, and therefore they ask, 'Are these performers of a Sattra?' Dear to people and noble is he who knows thus. vii. 2. 10. This (rite) with a Vaiçvanara on one side (only) was not able to win the world of heaven; it was stretched upwards and the gods piled round this Vaiçvanara, to overcome the world of heaven. The seasons made Prajapati sacrifice with it, and in them because of it he prospered. He prospers among the priests who knowing thus sacrifices with (the rite) of twelve days. They were desirous of obtaining (their desires) from him. He gave to the spring the sap [1], to the hot season barley, to the rains plants, to autumn rice, beans and sesamum to winter and the cool season. Prajapati made Indra sacrifice with it. Then indeed did Indra become Indra; therefore they say, 'It is the sacrifice of the inferior', for he by it first sacrificed.