I was watching Pride and Prejudice when I noticed that people are doing lots of drinking and the ball is rather long. So where would a person, especially a woman, in a similar ball (huge ball at a big palace-like house, but not an actual palace, in province, Regency era, England) go to pee? What about other balls in literature (Count of Monte Cristo's ball at the suburbs of Paris comes to mind)?
There's always more to be said on the subject of bathrooms, but perhaps this older thread -- in particular the post from u/colevintage -- may be of use to you.