Bhagavatapurana 8.7.6

8.7.6

kṛtasthānavibhāgāsta evaṃ kaśyapanandanāḥ /
mamanthuḥ paramaṃ yattā amṛtārthaṃ payonidhim //

5 & 6. Putting on a smile, He left off the fore part and took hold of the tail, the Immortals following Him. Having thus appointed places for themselves, the sons of Kasyapa churned the sea of milk for Amrita putting forth all their strength and attention; when the sea was being (thus) churned, the unsupported mount went down into the water.