"Fudochi Shinmyo Roku" (The Miracle of Immovable Wisdom), which compiled letters which Takuan had sent to Munenori YAGYU, is well-known as the one preaching 'Kenzen ichimi' (The Sword and Zen are One).
沢庵が柳生宗矩に与えた書簡を集めた『不動智神妙録』は、「剣禅一味」を説いたものとして著名である。