Śatapatha Brāhmaṇa ("of a hundred paths") 2.5.2.39

2.5.2.39

athādhvaryureva kāyena | ekakapālena puroḍāśena pracarati kāyenaikakapālena puroḍāśena pracaryādhvaryurevāhāgnaye sviṣṭakṛte 'nubrūhīti sa sarveṣāmeva haviṣāmadhvaryuḥ sakṛtsakṛdavadyatyathaitasyā eva payasyāyai pratiprasthātā sakṛdavadyatyathopariṣṭāddvirājyasyābhighārayatastā ubhāvevātikrāmato 'tikramyāśrāvyādhvaryurevāhāgniṃ sviṣṭakṛtaṃ yajeti tā ubhāveva vaṣaṭkṛte juhutaḥ

The Adhvaryu then proceeds with the cake on eleven potsherds for Ka; and having made that offering, he says, 'Pronounce the invitatory prayer to Agni Svishtakrit (" the maker of good offering")!' The Adhvaryu then takes cuttings from all (his) oblations, one from each; and the Pratiprasthâtri also takes one cutting from that oblation of curds (to the Maruts). They then pour twice butter upon (the portions), and step across (to the south side of the fires). On stepping across and calling for the 'Sraushat,' the Adhvaryu says, 'Pronounce the offering-prayer to Agni Svishtakrit;' and after the (concluding) 'Vashat,' they both pour out the oblation.