Kautilya's Arthashastra 14.1.2

14.1.2

kālakūṭādir viṣavargaḥ śraddheyadeśaveṣaśilpabhāṣābhijanāpadeśaiḥ kubjavāmanakirātamūkabadhirajaḍāndhacchadmabhir mlecchajātīyair abhipretaiḥ strībhiḥ pumbhiś ca paraśarīropabhogeṣv avadhātavyaḥ //

IN order to protect the institution of the four castes, such measures as are treated of in secret science shall be applied against the wicked. Through the instrumentality of such men or women of Mlechchha class as can put on disguises, appropriate to different countries, arts, or professions, or as can put on the appearance of a hump-backed, dwarfish, or short-sized person, or of a dumb, deaf, idiot, or blind person, kálakúta and other manifold poisons should be administered in the diet and other physical enjoyments of the wicked. Spies lying in wait or living as inmates (in the same house) may make use of weapons on occasions of royal sports or musical and other entertainments. Spies, under the disguise of night-walkers (rátrichári) or of fire-keepers (agni-jívi) may set fire (to the houses of the wicked).