Hokuzansho (Manual on Courtly Etiquette)

The manuscript Hokuzansho, vol. X, is the only surviving portion of the record of annual events in the Imperial Palace, affairs of state, and other matters which was kept by Fujiwara Kinto (966-1041). The two letters in kana among the twenty-five thousand documents found on the reverse side were written during the several years preceding 1001. They are truly invaluable as the oldest extant letters in kana and as proof that continuous cursive script in kana-gana had developed by that time.

— Museum description: Kyoto National Museum (CC BY 4.0), via ColBase / Japan Search.