Sei Shonagon's Pillow Book represents the rival salon of Empress Teishi. Like many of the other diaries by court women, the Pillow Book can be seen as a memorial to the author's patron, specifically a homage to the Naka no Kanpaku family and a literary prayer to the spirit of the deceased empress Teishi. The roughly three hundred discrete sections of the Pillow Book can be divided into three types such as list, essay, and diary, which sometimes overlap. The Pillow Book is now considered one of the pillars of Heian vernacular court literature, but unlike the Kokinshu, The Tales of Ise, and The Tale of Genji, which had been canonized by the thirteenth century, the Pillow Book was not a required text for waka poets and was neglected in the Heian and medieval periods. But it became popular with the new commoner audience in the Tokugawa period, and it has been read for its style, humor, and interesting lists.