Garudapurana 1.19.24

1.19.24

a ā nyasettu pādāgre i ī gulaphe 'tha jānuni /
u ū e ai kaṭitaṭe o nābhau hṛdi au nyaset //

One should place "a ā" at the tip of the foot; "i ī" at the ankle, then at the knee; / "u ū, e ai" on the waist; "o" at the navel; one should place "au" at the heart;