Ulrich Rülein von Calw's Leather Mining Apron

Origins
Ulrich Rülein von Calw was a scientist and mining engineer in Germany from the 1490s up to 1523.

Effects
All skin covered by apron becomes as tough as coal and the wearer becomes immune to weight on their covered skin, coal dust, and extreme pressure (e.g. underground pressure). The wearer also becomes extremely flammable, and can catch on fire when exposed to temperatures higher than 100 degrees Celsius (212 Fahrenheit).