I am trying to think of a book that we purchased at a homeschool conference when I was a kid (early 2000s). I seem to remember the setting being an aristocrat Russian household, and my vivid memory is of a boy (maybe a servant) trying to get rid of warts by using a frog at midnight… this is perhaps in the setting of a prank? But I think the main protagonist was female. I’d love to figure this out!