The Tales of Ise
According to the Man'yōshū (The Anthology of Ten Thousand Leaves), the first Saiō to serve at Ise was Princess Ōku, daughter of Emperor Tenmu, during the Asuka period of Japanese history. Mention of the Saiō is also made in the Aoi, Sakaki and Yugao chapters of The Tale of Genji, as well as in the 69th chapter of "The Tales of Ise" ("Ise Monogatari").