Moromoto wrote down the conversation he had with Tadasane in "Chugaisho," which became famous as a valuable historical manuscript that told of aristocratic society during the period of the government by the Retired Emperor (the title of the manuscript is derived by taking '中' (Naka) from Nakahara and '外' from Daigeki).
忠実との会話を師元が筆録した『中外抄』は、院政期の公家社会の様子を克明に伝える史料の一つとして名高い（同書の書名は中原の「中」と大外記の「外」から各々一字を取ったもの）。