[mettamage]

I don't think so. I know that he was interested in Buddhist stuff (source: some documentary).

But when I talked to him, he told us (part of the Radboud experiment in 2014, I think) that he just jumped into cold water and was forced to learn how to breath in such a way that he wouldn't freak out.

Note/edit: As you can see from my writing my memory isn't pinpoint accurate. Given that the article was published in 2014 [1], I'm sure I'm probably wrong in the year when I talked to him as it then most likely would've been April 2013 since I had to keep the results of the study a secret for at least a year.

[1] https://www.pnas.org/content/111/20/7379

[prox]

I am quite sure he mentioned it as inspiration (or he even learned it somewhere, on that count I am not sure) in some interview.

Things do not exist in a vacuum, though. Especially something such as breath would be pretty universal despite in what cultural context.