Shatapatha Brahmana 4.3.5.18

4.3.5.18

sa mekṣayati | vivasvannādityaiṣa te somapīthastasminmatsvetyathonnetra upāṃśusavanam prayacatyathāhonnetāramāsṛja grāvṇa iti tānādhavanīye vāsṛjati camase vā

He mixes it with (Vâg. S. VIII, 5), 'O Âditya Vivasvat, this is thy draught of Soma: feast thou upon it!' Thereupon he hands the Upâmsusavana to the Unnetri. Then he says to the Unnetri, 'Drop in the pressing-stones!' He drops them either into the Âdhavanîya or into a cup.