Kautilya's Arthashastra 12.2.16

12.2.16

tasyaiva paricārakavyañjanopadiṣṭaḥ siddhavyañjanaḥ sāṃvadanikīm oṣadhīṃ dadyāt "vaidehakaśarīre 'vaghātavyā" iti //

A spy, under the guise of a merchant, may, under the plea of winning the love of an immediate maid-servant of the beautiful queen (of the enemy), shower wealth upon her and then give her up. A spy in the service of the merchant may give to another spy, employed as a servant of the maid-servant, some medical drug, telling the latter that (in order to regain the love of the merchant), the drug may be applied to the person of the merchant (by the maid-servant). On her attaining success (the maid-servant) may inform the queen that the same drug may be applied to the person of the king (to secure his love), and then change the drug for poison.