Manasara 18.97

18.97

tuṅge vedāṃśakaṃ vyāsaṃ pañcāṃśaṃ corvī kathyate
tuṅge guṇāṃśa vedāṃśaṃ vistāraṃ gotramīritam

with four parts in height and five parts in width, it is declared as Urvī;
with three parts in height and four parts in width, it is spoken of as Gotrā;