Kautilya's Arthashastra 9.6.73

9.6.73

vītaṃsagilavac cārīn yogair ācaritaiḥ śaṭhaḥ /
ghātayet paramiśrāyāṃ viśvāsenāmiṣeṇa ca //E

When the country is full of local enemies, they may be got rid of by making them drink poisonous (liquids); an obstinate (clever) enemy may be destroyed by spies or by means of (poisoned) flesh given to him in good faith.