Wim hof,
what do you guys think of him? He seems to be the first who was able to influence his own autonomous nervous system, and he let's himself be studied by science.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4034215/
I like this
although...3 persons drowned after trying his breathing exercices near a pool, which they caution you not to do that near a dangerous place. Seems those breathing techniques are a bit heavy