[Kelamir]

There's the paper: “Brain over body”–A study on the willful regulation of autonomic function during cold exposure (DOI:10.1016/j.neuroimage.2018.01.067)

From the abstract:

"Our results provide compelling evidence for the primacy of the brain (CNS) rather than the body (peripheral mechanisms) in mediating the Iceman’s responses to cold exposure. They also suggest the compelling possibility that the WHM might allow practitioners to develop higher level of control over key components of the autonomous system, with implications for lifestyle interventions that might ameliorate multiple clinical syndromes."

I was doing cold exposure for a while, plunging palms and heels into water with ice. At first I could hold it a little there, but the duration was increasing with time. It's comfy to do while using laptop, mind doesn't focus on the hell going below :)