Śatapatha Brāhmaṇa ("of a hundred paths") 7.4.1.8

7.4.1.8

yadveva puṣkaraparṇamupadadhāti | āpo vai puṣkaraṃ tāsāmiyam parṇaṃ yathā ha vā idam puṣkaraparṇamapsvadhyāhitamevamiyamapsvadhyāhitā seyaṃ yoniragneriyaṃ hyagnirasyai hi sarvo 'gniścīyata imāmevaitadupadadhāti tāmanantarhitāṃ satyādupadadhātīmāṃ tatsatye pratiṣṭhāpayati tasmādiyaṃ satye pratiṣṭhitā tasmādviyameva satyamiyaṃ hyevaiṣāṃ lokānāmaddhātamām

And, again, why he puts down a lotus-leaf;--the lotus means the waters, and this earth is a leaf thereof: even as the lotus-leaf here lies spread on the water, so this earth lies spread on the waters. Now this same earth is Agni's womb, for Agni (the fire-altar) is this earth, since thereof the whole Agni is built up: it is this earth he thus lays down. He lays it down so as not to be separated from the truth: he thereby establishes this earth on the truth;--hence this earth is established on the truth; and hence the truth is this earth, for this earth is the most certain of these worlds.