In ancient Rome, the general rule was that slaves could be tortured freely. In fact, it was strongly suggested that any free man accused of a crime should have his slaves tortured, often executed, at his place before a verdict could be reached. But that didn’t stop the Roman elite from torturing the free men and women of their country. Roman law always had loopholes, and the elite rulers took advantage of every loophole.
Executioners often used animals to carry out their barbarity, as was the case with the cauldron torture. For this particular cruelty, a starved animal, such as a rat, a dog, or a cat, was placed inside a small cauldron. The opening of the cauldron was then fastened to the belly of the accused.
The executioner would hold a flame to the back of the cauldron, making the inside extremely hot. The animal would panic and try to escape. The only soft “ground” for it to dig its way out was through the belly of the accused.