Garudapurana 1.197.39

1.197.39

svabījaṃ mūrtirūpantu prāguktaṃ pārakalpayet /
yaṃ vāyumūlaṃ nairṛtye rephastvanalasaṃsthitaḥ //

One should imagine one's own seed-syllable in bodily form as spoken before: / 'yaṃ' the root of wind in the southwest, and the letter 'ra' situated in fire;