Shatapatha Brahmana 6.4.1.9

6.4.1.9

taduttaraṃ kṛṣṇājinādupastṛṇāti | yajño vai kṛṣṇājinamiyaṃ vai kṛṣṇājinamiyamu vai yajño 'syāṃ hi yajñastāyate dyauṣpuṣkaraparṇamāpo vai dyaurāpaḥ puṣkaraparṇamuttaro vā asāvasyai

He spreads it over the black antelope skin; for the black antelope skin is the sacrifice; and the black antelope skin is this earth, and the sacrifice is this earth, for on this earth the sacrifice is spread. And the lotus-leaf is the sky; for the sky is the waters, and the lotus-leaf is the waters; and yonder sky is above this earth.