Math Forum / Mathematics / Undergraduate Math / June 2007

Models for life drawing classes are often entirely nude, apart from
inconspicuous personal items such as small jewelry. In a job
advertisement seeking nude models, this may sometimes be referred to
as being "undraped". In Western countries, there is generally no
prohibition on the sexes posing nude for or drawing members of the
opposite gender, although this was not always the case in the past.

http://modelsnude.blogspot.com/