Śatapatha Brāhmaṇa ("of a hundred paths") 7.5.2.9

7.5.2.9

sapta pratyasyati | sapta vai śīrṣanprāṇāstānasminnetaddadhātyatha yadi pañca paśavaḥ syuḥ pañcaiva kṛtvaḥ sapta-sapta pratyasyetpañca vā etānpaśūnupadadhāti sapta-sapta vā ekaikasminpaśau prāṇāstadeṣu sarveṣu prāṇāndadhāti

Seven (chips) he thrusts into each,--seven vital airs there are in the head: these he thereby puts into it. And if there are five victims, let him thrust in five times seven (chips); for those five victims he puts on (the fire-pan), and there are seven vital airs in each victim: he thus puts the vital airs into all of them.