Yājñavalkya Śikṣā 16

16

mayūrastu trimātrāṃ vai mātrāṇāmiti saṃsthitiḥ
varṇo jātiśca mātrā ca gotraṃ chandaśca daivatam

the peacock indeed [sounds] three morae; such is the state of morae. / Speech sound, social class, mora, lineage, metre, and deity—