100% serious. Also using similar methods, I can withstand cold 0 celsious for several hours and just sit on a computer and read, wearing just shorts nothing else. Nowadays though, getting older, it starts to be a little bit challenging.

Some years back, I sat in freezing cold, 12 hours a day, wearing almost nothing and just reading. The more I can withstand cold, the better my eyes work.

You really have a great writing style - if this is an advertisement for your blog, it worked.