I may have told this story before, but back in 1978 Chuck Pease and I were with a Swiss team of 4 cavers in a winter expedition in Holloch in Switzerland. Our bivouac was 2 km from the entrance and about 500m below the mountains surface. Temperature was about 2-4C. In those days we all used carbide as we would be spending 4-6 days underground. The spent carbide was dumped in a pile at the bottom of a small canyon also used for a latrine. I know, I know, but that's how the European cavers did it back then. The theory being the spent carbide would chemically reduce the smell of the human waste.
Anyway, at the top of the canyon was the ledge where you stoop with your butt over the side and do your business. Hanging from the ceiling was a line with a stick at the end to hold a roll of toilet tissue. You also held onto this line while you were squatting for safety.
Well, I walked the 100m or so over to the latrine and noticed the line was no longer attached to the cave roof. Hmmmmmm...I looked down into the canyon (about 2m deep) and saw the white spent carbide had a pattern in it like someone had made a snow angel. Get the picture? The line was down there, too. Can you imagine the panic of the guy as he realized he was falling backwards into a pile of crap and spent carbide?
I went back to the bivouac where everyone was seated around a table drinking hot tea and asked who had fallen. No one would admit to and to this day the guilty party has not come forward.
We all had a good laugh about it, tho.