Such a technique of consuming minute amounts of poison over a course of time to gain immunity to the venom is also described in Chanakya's ArthaShastra. Chanakya was the prime minister in the Indian emperor Chandragupta Maurya's Magadha kingdom. This was around 300 BC. In order to develop espionage capabilities, it is strategy employed in developing these "Vishkanya" - poison women loosely.
Chanakya's ArthaShastra has been wrongly described as similar to Machiavellian works which deals with only espionage & subverting a rival power. The Arthashastra deals with that, but that is only 5-10% of the whole. The remaining parts of Arthashasrtra describes an entire economic model for nations / kingdoms to follow, the duties of a king, how to deal with rebellion etc - many, & almost all still applicable to modern society.
Chanakya's ArthaShastra has been wrongly described as similar to Machiavellian works which deals with only espionage & subverting a rival power. The Arthashastra deals with that, but that is only 5-10% of the whole. The remaining parts of Arthashasrtra describes an entire economic model for nations / kingdoms to follow, the duties of a king, how to deal with rebellion etc - many, & almost all still applicable to modern society.