Matsya Purana 255.3

255.3

aśītyaṃśaḥ pṛthutvaṃ syādagreṇāvaguṇaiḥ saha.
rucakaścaturaḥ syāttu aṣṭāsro vajra ucyate .. 255.2

Sûta said — ' Now I shall tell you the measurements of the pillars " Multiply the alitude of the house by 7 (seven) which divided by 80 (eighty) will give the breadth of the pillars If the pillars be square, they are known as ruchaka and if they be octagonal they are called Vajra—1-2