There was a time when geishas were considered modern symbols, much like haute couture is nowadays. "Average women wanted to emulate them, so someone wrote everything down," Tsai explains. "Back in the day, there weren't department stores or beauty brands, so in order to do something for their skin, they had to use what was within reach." This mean they became quite the skilled DIY-ers, using ingredients from their kitchen or their local herbalist and utilizing teachings from Traditional Chinese Medicine, which had just traveled to Japan. When Tsai found the only written account of geisha beauty rituals, she was surprised by what the translator told her. "You would think their secret would be a rare flower that only blooms at midnight, or something like that," she says. "But their ingredients were super simple—it's basically just incorporating all the elements of the traditional Japanese diet." Think about the traditional dinner: it would most likely include sushi—which is made with rice, seaweed, and fish—and green tea. And…that's basically the basis of their entire skincare ritual. "Green tea has an antioxidant in it called EGCG, which is a particular kind of antioxidant that is especially efficient at neutralizing the kind of free radical damage caused by the sun," Tsai explains. "It's very good for your skin." Like the teachings of Traditional Chinese Medicine, a geisha's approach to skincare is a very inside-out approach, with a combination of diet and lifestyle changes. They make topical beauty treatments that often mirror what they ate. So, for example, rice: it might seem like just a carb, but the husk (which the Japanese call komonuka) stores a potent combination of antioxidants, moisturizers, UV absorber, and brighteners for the skin. (This is the basis for Tatcha's Classic Rice Enzyme Powder ($25).
Seaweed and squalane are two more ingredients often used in a geisha's skincare routine. Tsai explains that seaweed have contain polysaccharides, which are basically little sponges that retain water so they don't dry out in salt water. This would explain why, when you use it on your skin, it keeps water from evaporating and is what Tsai calls a "miraculous moisturizer." Squalane is an ingredient that used to come from shark liver oil, which is identical to the oil that's already in your skin when you are baby; in fact, supposedly 13% of your skin is made of this oil when you're an infant. Tsai says that nowadays, you can get squalane from olives—it's molecularly identical.