Śatapatha Brāhmaṇa ("of a hundred paths") 10.6.5.3

10.6.5.3

sa tredhātmānaṃ vyakuruta ādityaṃ tṛtīyaṃ vāyuṃ tṛtīyaṃ sa eṣa prāṇastredhāvihitastasya prācī dikśiro'sau cāsau cermāvathāsya pratīcī dikpucamasau cāsau ca sakthyau dakṣiṇā codīcī ca pārśve dyauṣpṛṣṭhamantarikṣamudaramiyamuraḥ sa eṣo'psu pratiṣṭhito yatra kva caiti tadeva pratitiṣṭhatyevaṃ vidvān

He made himself threefold--(Agni being one-third), Âditya one-third, and Vâyu one-third: that is this threefold breath. The eastern quarter was his head, this and that (intermediate quarters) are his fore-feet, the western quarter his tail, this and that (intermediate quarters) his thighs, the southern and northern quarters his flanks; the sky his back, the air his belly, and this (earth) his chest:--on the waters he was established any and everywhere, and so indeed is he established who knows this.