Amy Tan was 200 pages into a new novel when she attended a large exhibition on Shanghai life in the early 1900s. While there, she bought a book she thought might help her as she researched details on life in the Old City. She stopped turning pages when she came upon a group portrait.

“It’s called the ’10 Beauties in Shanghai,’ ” she says. These were the winners of a citywide beauty contest for courtesans. There, staring solemnly at the reader, were 10 young women, half of them dressed in similar outfits — snug silk jackets with high, fur-lined collars and three-quarter-length sleeves that displayed long, white sleeves underneath. Several of the women were wearing tight headbands embroidered with pearls. The shape of the headbands brought the wearer’s forehead to a comely V shape, and the tension pulled the eye upward, into the much-desired Phoenix eye shape. The wardrobe and the look were all part of the courtesan’s official ensemble.