In the middle ages - it is said - there was such a thing as trial by ordeal.
Simply put (in the law of Athelstan, ruler of England 924 to 927)
1. You are accused of a crime
2. You need to prove you are innocent
3. You plunge one hand in boiling water and retrieve a stone from the bottom of the vessel.
There's a tariff. 1 accuser = up to the wrist. 3 accusers = up to the elbow.
If your burns started to heal after three days then you are judged innocent.
Ironically, Athelstan means "noble stone".
If this was ever really applied then I can't conceal my contempt for such a way of thinking. How could anyone even begin to believe (or perhaps just cynically suggest to others) that such a process would reveal truth?
In the modern age a physicist reinvented this idea of ordeal, but he was not on trial. The accusation went the other way now. Science and truth were attacking irrationality and fear. The accuser - Jearl Walker - plunged his hand into not just boiling water but molten lead, to support rational thought.
Jearl Walker wrote a column in Scientific American for many years. I always read it eagerly. I remember well, after perhaps 30 years, his description of how he thought the laws of physics would let him plunge a hand into molten lead without injury.
He said something like (from half a life-time's recollection) "I checked my calculations one final time, and they were correct. I felt a little fear, but trusted science, went ahead - and science was right was right, as I thought it would be."
A test of faith.
Jearl Walker is alive and well. You can see his demonstration of faith repeated here. Do watch.
Remember to spit on your finger before you test your iron!
If you travel back in time to 10th century England and are subjected to trial by ordeal, spitting on you hands won't work of course. I'm not sure what would.