Garudapurana 2.15.70

2.15.70

grīvā skandhau dvitīye ca tṛtīye hṛdayaṃ bhavet /
caturthena bhavetpṛṣṭhaṃ pañcame nābhireva ca //

on the second, the neck and shoulders; on the third, the heart is formed; / by the fourth, the back is formed; and on the fifth, the navel;