Śatapatha Brāhmaṇa ("of a hundred paths") 8.2.3.10

8.2.3.10

mūrdhā vaya iti | prajāpatirvai mūrdhā sa vayo 'bhavatprajāpatiścanda iti prajāpatireva cando 'bhavat

[He lays down four in front, with, Vâg. S. XIV, 9], 'The head is vigour,'--Pragâpati, doubtless, is the head: it is he that became vigour;--'Pragâpati the metre,'--Pragâpati indeed became a metre.