Kautilya's Arthashastra 9.6.32

9.6.32

tad asya vaidehakavyañjanāḥ śatrumukhyeṣu vikrīṇīran //

The conqueror may gather some merchandise peculiar to his enemy's country and unknown elsewhere. Spies, under the garb of merchants, may sell that merchandise to other important enemies and tell them that that merchandise was given (to the conqueror) by the enemy (whose country's product it is).