The back of the Lord is the place for all kinds of frustration and ignorance, as well as for immorality. From His veins flow the great rivers and rivulets, and on His bones are stacked the great mountains.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
अव्यक्तरससिन्धूनां भूतानां निधनस्य च । उदरं विदितं पुंसो हृदयं मनसः पदम्
avyaktarasasindhūnāṃ bhūtānāṃ nidhanasya ca | udaraṃ viditaṃ puṃso hṛdayaṃ manasaḥ padam
SB 2.6.10