Kautilya's Arthashastra 5.2.67

5.2.67

karmakaravyañjano vā gṛhe karma kurvāṇaḥ stenakūṭarūpakārakopakaraṇam upanidadhyāt, cikitsakavyañjano vā garam agadāpadeśena //

Or a spy, under the garb of a goldsmith, may undertake to do some work in the house of a seditious person, and gather in his employer's house such instruments as are necessary to manufacture counterfeit coins.

A spy, under the garb of a physician, may declare a healthy person of seditious character to be unhealthy (and administer poison). Or a spy, attending as a servant upon a seditious person may not only call for an explanation from another fraudulent spy as to how certain articles necessary for the installation of a king and also the letters of an enemy came into the possession of his master, but also volunteer an explanation himself.