Matsya Purana 249.26

249.26

kalpyatāṃ netrakārye yaḥ śaktaḥ syādveṣṭane mama.
tatastu nirgatau devau kūrmaśeṣau mahābalau .. 249.26 ..

In accepting their prayer, the lord of the mountains said "I shall be the churning stick, and let some one who may be strong enough to volunteer himself to act as a receptacle, on which I can revolve, then I will be able to churn the ocean, also the Śeṣa serpent to coil round the stick. Afterwards the most valiant turtle and Śêṣa endowed with 1/4 of Viṣṇu's power, went to support the Earth, and haughtily the Turtle said—"When I can easily hold all the three regions on my back, how can I feel the weight of this Mandara mountain ?'—25 28