Manasara 12.97

12.97

tatsamaṃ cādhikaṃ vāpi ceṣṭakāyāmamiṣyate
vistārārdhaṃ ghanaṃ kuryātamaṃ tu caturaṣṭakam

or equal to that, or greater, is desired for the length of the brick. / Half the width one should make its thickness; its [face] should be quadrangular.