Shatapatha Brahmana 8.7.1.19

8.7.1.19

atha madhyamāyai svayamātṛṇāyai | upariṣṭādviśvajyotiṣamupadadhātyantarikṣaṃ vai madhyamā svayamātṛṇā vāyurmadhyamā viśvajyotirantarikṣe tadvāyuṃ dadhāti tasmādayamantarikṣe vāyuḥ

And the (second) Visvagyotis he lays down subsequent to the second naturally-perforated one (in the third, or central) layer; for the second naturally-perforated one is the air, and the second Visvagyotis is Vâyu (the wind): he thus places the wind in the air, whence that wind (has his abode) in the air.