Its collection of ancient documents includes the 'To-ji Hyakugo Monjo Document,' a National Treasure, which had been handed down at To-ji Temple (also known as Kyogokoku-ji Temple) that is associated with Kukai, a well-known Buddhist priest, in Minami-ku Ward of Kyoto City, and 'Ancient documents and books of Kanchiin Temple' that had been handed down at Kanchiin Temple, a sub temple of To-ji Temple, and 'Kawashimake Bunsho' (the Kawashima family documents), which are both designated as Important Cultural Properties.
古文書関係では、京都市南区にある空海ゆかりの寺院・東寺（教王護国寺）に伝来した国宝の「東寺百合文書」をはじめ、東寺の子院・観智院に伝来した「観智院伝来文書典籍類」、「革嶋家文書」が重要文化財に指定されている。