Shatapatha Brahmana 4.1.1.28

4.1.1.28

athopāṃśusavanamādatte | taṃ na daśābhirna vivitreṇopaspṛśati yathā hyadbhiḥ praṇiktamevaṃ tadyadyaṃśurāśliṣṭaḥ syātpāṇinaiva pradhvaṃsyodañcamupanipādayedvyānāya tveti vyāno hyasyaiṣaḥ

He then takes the Upâmsu-savana (pressing-stone). He neither touches it with the fringe nor with the straining-cloth, for that would be like rinsing it in water. If there be any spray adhering to it, let him remove it with his hand, and then lay down (the stone) beside (the Upâmsu cup), with the face towards the north, with, 'Thee for the through-breathing!' for this (stone) is indeed his (Yagña's) through-breathing.