Śatapatha Brāhmaṇa ("of a hundred paths") 2.5.2.37

2.5.2.37

athādhvaryurevāha varuṇāyānubrūhīti | sa upastṛṇīta ājyamathāsyai vāruṇyai payasyāyai dviravadyati so 'nyatareṇāvadānena saha meṣamavadadhātyathopariṣṭādājyasyābhighārayati pratyanaktyavadāne atikrāmatyatikramyāśrāvyāha varuṇaṃ yajeti vaṣaṭkṛte juhoti

The Adhvaryu now says (to the Hotri), 'Pronounce the invitatory prayer to Varuna!' He then pours an 'under-layer' of butter (into the guhû), takes two cuttings from Varuna's curds, and with either of the two cuttings puts the rant (in the spoon). He then pours butter thereon, replenishes (the place whence) the two cuttings (have been made), and steps across (to the south side of the fire). After stepping across and calling for the 'Sraushat,' he says (to the Hotri), 'Pronounce the offering-prayer to Varuna!' and, on the 'Vashat' being uttered, he pours out the oblation.