The Pillow Book is a book of observations and musings recorded by Sei Shonagon during her time as court lady to Empress Consort Teishi during the 990s and early 1000s in Heian Japan. The book was completed in the year 1002. In it she included lists of all kinds, personal thoughts, interesting events in court, poetry, and some opinions on her contemporaries. While it is mostly a personal work, Shonagon's writing and poetic skill makes it interesting as a work of literature, and it is valuable as a historical document. Part of it was revealed to the Court by accident during Shonagon's life.