Śatapatha Brāhmaṇa ("of a hundred paths") 4.6.1.5

4.6.1.5

sa vai tūṣṇīmeva grāvāṇamādatte | tūṣṇīmaṃśūnnivapati tūṣṇīmapa upasṛjati tūṣṇīmudyatya sakṛdabhiṣuṇoti tūṣṇīmenamanavānanjuhoti tadenam prajāpatiṃ karoti

Silently he takes up the pressing-stone; silently he throws down the Soma-plants (amsu); silently he pours water thereon; silently raising (the stone), he presses once; silently he offers that (libation) without drawing breath: thus he makes him (the sacrificer) to be Pragâpati.