Śatapatha Brāhmaṇa ("of a hundred paths") 8.1.4.2

8.1.4.2

tadāhuḥ | yadayam puro bhuvo 'yaṃ dakṣiṇā viśvakarmāyam paścādviśvavyacā idamuttarātsvariyamupari matiriti samprati diśo 'bhyanūcyante 'tha kasmādenā akṣṇayādeśeṣūpadadhātīti prāṇā vai prāṇabhṛtastā yatsamprati diśa upadadhyātprāgapaṃ haivāyam prāṇaḥ saṃcaredatha yadenā evamabhyanūktāḥ satīrakṣṇayādeśeṣūpadadhāti tasmādayam prāgapam prāṇaḥ sannakṣṇayā sarvāṇyaṅgāni sarvamātmānamanusaṃcarati

Here now they say, 'Whereas in (the formulas) "This one, in front, the existent--this one, on the right, the all-worker--this one, behind, the all-embracer--this, on the left, heaven--this one, above, the mind"--they (these bricks) are defined as exactly opposite the quarters, why, then, does he lay down these (bricks) in sidelong places?' Well, the Prânabhritah are the vital airs; and if he were to place them exactly opposite the quarters, then this breath would only pass forward and backward; but inasmuch as he now lays down these (bricks) thus defined in sidelong places, therefore this breath, whilst being a backward and forward one, passes sideways along all the limbs and the whole body.