To decide which manuscript should be classified into which group, IKEDA took seriously the outward form of the manuscript such as Okugaki (the part of the manuscript having information such as who made a copy, when it was made, which book it was copied from, etc.)
但し、池田はそれぞれの写本をどの分類に入れるかを決めるに当たってはそれぞれの写本の奥書（その写本がどのような写本からいつ誰によってどのように写されたのかといったことを記してある部分）の内容等のそれぞれの写本の外形的なものを重視した。