Kautilya's Arthashastra 13.2.16

13.2.16

jaṭilavyañjanam antarudakavāsinaṃ vā sarvaśvetaṃ taṭasuruṅgābhūmigṛhāpasaraṇaṃ varuṇaṃ nāgarājaṃ vā sattriṇaḥ kramābhinītaṃ rājñaḥ kathayeyuḥ //

Any person, disguised as an ascetic and living under water or in the interior of an idol entered into through a tunnel or an underground chamber, may be said by his disciples to be Varuna, the god of water, or the king of snakes, and shown to the king. While going to accomplish whatever the king may desire, the latter may be requested to come and remain... (as before.)