In the Agniṣṭoma (Agnishtoma) yāga (yaga), the formal first day of worship is called sutyādina (sutyadina). On the fourth day of the rite, Āhavaniya (Ahavaniya) Agni placed on the east of the aiṣṭika (aishtika) platform is brought to the āgnīdhrīyaset up on the saumika platform. On the next day, i.e. sutyādina, the same fire from the āgnīdhrīya dhiṣñya is used to light fire in other dhiṣñya. After purchasing the somalatā (somalata), it is preserved in the ancient family house. This somalatā too needed to be taken along with Agni and placed in the havirdhāna (havirdhana) pavilion. The next day the somalatā would be crushed and its sap would be extracted for the sacrificial rite. The procedure thorugh which addhvaryu (the priest of Yajurveda) carried Agni and somalatā eastwards, first to the āgnīdhrīya and then to the havirdhāna pavilion, is known as agniṣomapraṇayana (agnishomapranayana). The term literally refers to the process of Agni and somalatā being carried eastwards. Pra means ‘eastwards’ and nayana means ‘to carry’. During the ritual of agniṣomapraṇayana, hotā or the priest of Ṛgveda recited hymns suited for the occasion.
[See Somayāga, Agnīdhra – 2]