Śatapatha Brāhmaṇa ("of a hundred paths") 7.5.2.40

7.5.2.40

āruhyāgniṃ jaghanena svayamātṛṇām parītyāpasyā upadadhāti | āpa etā yadapasyā atha vā etebhyaḥ paśubhya āpa utkrāntā bhavanti tadyadapasyā upadadhātyeṣvevaitatpaśuṣvapo dadhātyanantarhitāḥ paśubhya upadadhātyanantarhitāstatpaśubhyo 'po dadhāti pañca-pañcopadadhāti pañca hyete paśavaḥ sarvata upadadhāti sarvata evaiṣvetadapo dadhāti

Having stepped on the altar and walked round behind the naturally-perforated (brick), he lays down the Apasyâh (water-bricks);--now the Apasyâh are the same as water, and the water has gone out of these victims: he thus puts water into these victims, when he lays down the Apasyâh (bricks). He lays them down close to the (heads of the) animals: he thereby puts the water together with the animals. He lays down five (bricks) in each quarter, for five are those victims. He lays them down in every (quarter): everywhere he thus puts water into them.