" A morsel of execration "
A piece of cheese or bread which was consecrated with a form of exorcism, desiring of God that it might cause convulsions and paleness, and find no passage if the person was really guilty, but might turn to health and nourishment if he was innocent.
This really comes across as a form of voodoo or ju ju, as adapted to 18th Century England. Perhaps even a culinary take on the witchs ducking stool?