Śatapatha Brāhmaṇa ("of a hundred paths") 8.3.4.3

8.3.4.3

atha yāḥ sapta paścāt | eṣāmevaitatprāṇānāmetānprāṇānpratīnkaroti tasmādyadebhirannamatti tadetairatyeti

And those seven which (he places) behind he thereby makes the counter-breathings to those (first breathings); and hence by means of (the channels of) these breathings he passes over the food which he eats with those (other) breathings.