Kautilya's Arthashastra 4.4.18

4.4.18

sa cet tathā kuryād rasada iti pravāsyeta //

Whoever is suspected of administering poison (rasa = mercury) to others by reason of his talking of it or selling or purchasing mercury, or using it in preparing medicines, may be approached with the tale that a certain enemy of the spy may be killed and that a certain amount of money may be received as reward. If he does so, he shall be proclaimed as a poisoner (rasada), and banished.