Shatapatha Brahmana 14.1.4.1

14.1.4.1

sa yadaitadadhvaryuḥ upottiṣṭhannāha rucito gharma iti tadupotthāyāvakāśairupatiṣṭhante prāṇā vā avakāśāḥ prāṇānevāsminnetaddadhāti ṣaḍupatiṣṭhante ṣaḍvā ime śīrṣanprāṇāstānevāsminnetaddadhāti

Now, when the Adhvaryu here steps up and says, 'The Gharma is aglow,' they step up and revere it (the Mahâvîra) with the Avakâsa; but the 'avakâsa' are the vital airs: it is thus the vital airs he lays into it. Six of them step up to it, for six in number are these vital airs in the head: it is these he thus lays into it.