Kautilya's Arthashastra 2.35.14

2.35.14

purāṇa coravyañjanāś cāntevāsinaś caityacatuṣpathaśūnyapadodapānanadīnipāna.tīrthāyatanāśramāraṇyaśailavanagahaneṣu stenāmitrapravīrapuruṣāṇāṃ ca praveśanasthānagamanaprayojanāny upalabheran //

In places where altars are situated or where four roads meet, in ancient ruins, in the vicinity of tanks, rivers, bathing places, in places of pilgrimage and hermitage, and in desert tracts, mountains, and thick grown forests, spies under the guise of old and notorious thieves with their student bands shall ascertain the causes of arrival and departure, and halt of thieves, enemies, and persons of undue bravery.