Śatapatha Brāhmaṇa ("of a hundred paths") 1.6.2.3

1.6.2.3

tercantaḥ śrāmyantaśceruḥ | śrameṇa ha sma vai taddevā jayanti yadeṣāṃ jayyamāsarṣayaśca tebhyo devā vaiva prarocayāṃ cakruḥ svayaṃ vaiva dadhrire preta tadeṣyāmo yato devāḥ svargaṃ lokaṃ samāśnuvateti te kim prarocate kim prarocata iti ceruretpuroḍāśameva kūrmam bhūtvā sarpantaṃ teha sarva eva menire yaṃ vai yajña iti

They went on praising and toiling; for by (religious) toil, the gods indeed gained what they wished to gain, and (so did) the Rishis. Now whether it be that the gods caused it (the sacrifice) to attract (or, peep forth to) them, or whether they took to it of their own accord, they said, 'Come, let us go to the place whence the gods obtained possession of the world of heaven!' They went about saying (to one another), 'What attracts? What attracts?' and came upon the sacrificial cake which had become a tortoise and was creeping about. Then they all thought, 'This surely must be the sacrifice!'