Many years ago, I modeled for an art class at my university. (They usually used women, as the students considered men too 'easy' to draw)

Women were allowed to model nude, but men were expected to wear some minimal covering, so I got the smallet 'posing brief' I could find...almost a thong.
Never again...uncomfortable and, as Kim C says, silly. (and I felt more exposed than if I had been naked!)