More can be written, but you might like to see "Are there many cases of a 'food taster' actually consuming poison and dying on the spot?". /u/jetpacksforall discusses Roman cases, and /u/RockyIV quotes about medieval practice (I can't get the previous pages in Google Books, so I can't be sure whether it's the court of the duke of Burgundy or not).

This is not to discourage discussion. More questions, data and debate are welcome.