Bhagavatapurana 2.1.19

2.1.19

tatraikāvayavaṃ dhyāyedavyucchinnena cetasā /
mano nirviṣayaṃ yuktvā tataḥ kiñcana na smaret /
padaṃ tat paramaṃ viṣṇormano yatra prasīdati //

19. There (then) he should contemplate but one member of the body with undivided attention; having restrained the mind from all external objects, he should not then think of anything else; and that is the highest form of Vishnu, at which (in contemplating which) the mind becomes rejoiced.