Kautilya's Arthashastra 5.2.68

5.2.68

pratyāsanno vā dūṣyasya sattrī praṇihitam abhiṣekabhāṇḍam amitraśāsanaṃ ca kāpaṭikamukhenācakṣīta, kāraṇaṃ ca brūyāt //

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.