Kautilya's Arthashastra 2.5.2

2.5.2

caturaśrāṃ vāpīm an-udakopasnehāṃ khānayitvā pṛthuśilābhir ubhayataḥ pārśvaṃ mūlaṃ ca pracitya sāradārupañjaraṃ bhūmisamaṃ tritalam anekavidhānaṃ kuṭṭimadeśasthānatalam ekadvāraṃ yantrayuktasopānaṃ bhūmigṛhaṃ kārayet //

Having dug up a square well not too deep to be moist with water, having paved both the bottom and the sides with slabs of stone, he shall, by using strong timber, construct in that well a cage-like under-ground chamber of three stories high, the top-most being on a level with the surface of the ground, with many compartments of various design, with floor plastered with small stones, with one door, with a movable staircase, and solemnised with the presence of the guardian deity.