The Book of Five Rings
The most famous exponent of "nitōjutsu" was Miyamoto Musashi (1584 – 1645), the founder of Hyōhō Niten Ichi-ryū, who advocates it in "The Book of Five Rings". "Nitōjutsu" is not however unique to Hyoho Niten Ichi-ryū, nor was "nitōjutsu" the creation of Musashi. Both Tenshin Shōden Katori Shinto-ryū were founded in the early Muromachi period (ca. 1447), and Tatsumi-ryu founded Eishō period (1504–1521), contain extensive two-sword curricula while also preceding the establishment of Musashi’s school.