Vishnupurana 2.12.32

2.12.32

hṛdi nārāyaṇaś cāste aśvinau pūrvapādayoḥ
varuṇaś cāryamā caiva paścime tasya sakthinī //

The celestial porpoise, in which Dhruva is fixed, has been mentioned, but you shall hear its constituent parts in more detail, as it is of great efficacy; for the view of it at night expiates whatever sin has been committed during the day; and those who behold it live as many years as there are stars in it, in the sky, or even more. Uttánapáda is to be considered as its upper jaw; Sacrifice as its lower. Dharma is situated on its brow; Náráyańa in its heart. The Áswins are its two fore feet;

and Varuńa and Áryamat its two hinder legs. Samvatsara is its sexual organ; Mitra its organ of excretion. Agni, Mahendra, Kaśyapa, and Dhruva, in succession, are placed in its tail; which four stars in this constellation never set.