Jaiminīya (Talavakāra) Brāhmaṇa 2-8.314

As to this they say: 'One should not undertake the Mahāvrata before a year.' In that there is a Pṛṣṭhya six-day rite, the pṛṣṭhas indeed are the seasons; the seasons are the year. The year ripens all proper food; they reach that very proper food conquered by the year. The Mahāvrata is twenty-five-fold; food indeed is the twenty-fifth [factor], [it is] for the attainment of proper food. There is the all-stoma Atirātra for the conquest and traversal of all worlds; for all this [universe] is indeed the stomas. Moreover, [thinking:] 'Having prospered together with those stomas that we have approached one by one, and having firmly stood in them, may we reach the conclusion!' Now, for one whose [rite] has the stomas of this Pṛṣṭhya six-day rite, the twenty-fourth day, the Viśvajit, and the Sarvapṛṣṭha Atirātra—one who should desire: 'May my Mahāvrata be approached indirectly,' he should sacrifice with this rite. In that it is the twenty-fourth day, thereby his Mahāvrata is approached indirectly. Furthermore, whatever hiṃ-sound or prastāva or pratihāra or whatever is there, thereby his twenty-fifth [entity] is attained. There is the Viśvajit Sarvapṛṣṭha Atirātra. Fortune indeed and the summit are the pṛṣṭhas; through the pṛṣṭhas they ascend to that very fortune and the summit.

Now, for one of whom the Jyotiragniṣṭoma is in the middle of this Pṛṣṭhya six-day rite, and the Jyotiratirātra

at the end—one who should desire: 'May one endowed with spiritual luster be born in my offspring,' he should sacrifice with this rite.

The Pṛṣṭhya six-day rite is indeed the body.