I was watching an old Burce Lee classic Enter the Dragon, where on it they showed martial arts students dipping their hands in what looked like metal bowls filled with gray rocks and sand type stuff, with fires under the bowls heating them. Does anyone know what they were doing here exactly and what they had int he bowls? Im guessing they were callousing their hands but im not sure, and im not sure what was in the bowls exactly. Maybe if there is an exact term for this, i dont know.