It also stores many autograph letters by emperors and historical prominent figures, documents related to the ceremonies in the Imperial Court, and a number of items of ancient copies of old tales and anthologies of Waka poems, many of which are not only valued as historical materials but also artifacts of the history of calligraphy.
また、天皇や歴史上の著名人の自筆書状、宮廷儀式関係、物語や和歌集の古写本なども多数収蔵し、歴史資料としてのみならず、書道史上の遺品としても貴重なものが多い。