Wim Hof has said something to the effect that he kept breaking Guinness World Records to draw peoples attention to a more spiritual dimension and this is what he is most into. His basic practices are some type of yoga but he doesn't go into detail about it and doesn't call his practice tummo. In his book he tells about using some kind of sanskrit mantra while withstanding cold in a wind tunnel and remembering past life as a yogi in India.
After doing his desert marathon without water he is now trying to convince western medicine into accepting the mind's ability to control the immune system:
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Here is another iceman who lived in the Soviet Union, Porfiri Ivanov, shown doing using cold water for health and also doing some type of healing:
Porfiri survived German concentration camp and being put into mental hospital by Soviets due to his "strange lifestyle" of never wearing anything but shorts even in Russian winter. I've read that his basic teachings on health(daily cold showers, fasting) has 10000+ followers in modern Russia.