I'm not sure if this is the same guy, but a Sherpa bivouacked overnight at the summit with no oxygen, just to show it can be done. Well, this was word of mouth

I'm not sure if this is the same guy, but a Sherpa bivouacked overnight at the summit with no oxygen, just to show it can be done. Well, this was word of mouth from a "Khumbhu doctor" (pro route-setter for the Khumbhu ice falls) when I was in the region years ago. The guy he was talking about had summited multiple times, and set all kinds of unofficial speed records for ascent + descent, but was kind of off the radar because he was on the worker side of the industry, not the sponsored climber side.