The Dreaming Age, by Yang Feiyun, 1999 [Photo/english.cgaurdian.com] The A4 waist challenge has gone viral online as girls post pictures of their A4 paper sized waists to show off their slim body. A thin waist is often considered as a symbol of beauty. Some artists who focus on the beauty of the female body love the A4 sized waist too. Let's have a look at famous paintings that feature "A4 waist models".