also: まくらそうし
private diary; pillow book
Archaic term for a personal diary or miscellany kept near the pillow, often containing reflections, anecdotes, and lists. The most famous example is Sei Shōnagon's 'The Pillow Book'.
Sei Shōnagon's Pillow Book is famous as a Heian-period essay collection.
book of erotic pictures
Historical use for a collection of erotic or pornographic illustrations, often kept discreetly.
During the Edo period, erotic books called 枕草紙 were secretly circulated.