Kautilya's Arthashastra 4.8.16

4.8.16

evam atisaṃdadhyāt, yathā vā nikṣepāpahāre vyākhyātam //

Among the spies such as harlots, suppliers of water and other drinks to travellers, story-tellers, hotel-keepers providing travellers with boarding and lodging, any one who happens to be acquainted with the work similar to that of the suspected may be let off to watch his movements, as described in connection with misappropriation of sealed deposits.