The first time Xia Boyu tried to climb Mount Everest, he lost his feet. It was 1975, and Boyu was headed up the mountain with a Chinese national mountaineering team. They had made it to about 28,215 feet, but that’s when a nasty winter storm set in. For two days and three nights the team endured subzero temperatures, made worse for Boyu, who decided to loan his sleeping bag to a fellow climber who had fallen ill. By the end of the unsuccessful climb, his feet were numb with severe frostbite, requiring amputation. Twenty years later, both of his legs would be amputated, too, after he developed lymphoma, a rare form of blood cancer. But none of that stopped Boyu from trying to climb Mount Everest again and again and again.