Kautilya's Arthashastra 2.27.30

2.27.30

saṃjñābhāṣāntarajñāś ca striyas teṣām anātmasu /
cāraghātapramādārthaṃ prayojyā bandhuvāhanāḥ //E

The wives of actors and others of similar profession who have been taught various languages and the use of signals (sanja) shall, along with their relatives, be made use of in detecting the wicked and murdering or deluding foreign spies.