Śatapatha Brāhmaṇa ("of a hundred paths") 1.2.1.16

1.2.1.16

atha śamyāmudīcīnāgrāmupadadhāti | diva skambhanīrasītyantarikṣameva rūpeṇāntarikṣeṇa hīme dyāvāpṛthivī viṣṭabdhe tasmādāha diva skambhanīrasīti

He now puts upon (the west side of) it the wedge with its point turned towards north, whilst muttering the text (Vâg. S. I, 19): 'The stay of the sky art thou!' that is to say, it represents the atmosphere; for by means of the atmospheric region those two, the sky and the earth, are firmly kept asunder; and for this reason he says, 'The stay of the sky art thou!'