Shatapatha Brahmana 9.3.1.20

9.3.1.20

atha yaṃ dvitīyaṃ dakṣiṇato juhoti | paśavaḥ sa sa saptakapālo bhavati sapta hi grāmyāḥ paśavastamanantarhitam pūrvasmājjuhotyapsu tatpaśūnpratiṣṭhāpayati

And the second (cake) which he offers on the right side, is animals; it is one of seven potsherds, for there are seven domestic animals. He offers it close to the preceding one (representing the rivers): he thus settles animals near water.