O son of the Pāṇḍu dynasty, when Mandara Mountain was thus being used as a churning rod in the Ocean of Milk, it had no support, and therefore although held by the strong hands of the demigods and demons, it sank into the water.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
मथ्यमानेऽर्णवे सोऽद्रिरनाधारो ह्यपोऽविशत् । ध्रियमाणोऽपि बलिभिर्गौरवात्पाण्डुनन्दन
mathyamāne'rṇave so'driranādhāro hyapo'viśat | dhriyamāṇo'pi balibhirgauravātpāṇḍunandana
SB 8.7.6