Daniel,
the earliest references i have to seen to dan ranks, as in "____ degree black belt" only go back to the 30's
interesting thing to research tho
edited to add
according to wiki, Kano used Dan rank.
Only one, Shodan.
there was no second degree, third degree, etc
that didnt happen till later
according to one source:
" In 1907, Kano introduced the modern judogi and its modern obi, but he still only used white and black belt ranks. The other colored belts originated later when Judo began being practiced outside of Japan. Sensei Mikonosuke Kaiwashi introduced various colored belts in Europe in 1935 when he started to teach judo in Paris.
The Judo practice uniform and belt system eventually spread to many of the other modern martial arts such as aikido and karate which adapted them for their purpose. Karateka in Okinawa didn't use any sort of special uniform at all in the old days. The kyu/dan ranking system, and the modern karategi (modified judogi) were first
adopted by Funakoshi in an effort to encourage karate's acceptance by the Japanese. He awarded the first shodan ranks given in karate to Tokuda, Otsuka, Akiba, Shimizu, Hirose, Gima, and Kasuya on April 10, 1924. "
but again, Funikoshi only awarded Shodan
then there is this:
"For its part, the Butoku-kai issued instructor's licenses: the titles renshi (the lowest), kyoshi, and hanshi (the highest). It would be a while before the dan/kyu system became universal in karate. By the end of the 1930s, each karate group was called upon to register with the butoku-kai for official sanctioning, and in 1938, a meeting of the Butoku-kai's official karatedo leaders was held in Tokyo. Its purpose was to discuss the standards for awarding rank within their art. Attending, among others, were Hironori Ohtsuka of wado-ryu, Kenwa Mabuni of shito-ryu, Kensei Kinjo (Kaneshiro) and Sannosuke Ueshima of kushin-ryu, Tatsuo Yamada of Nippon kempo, Koyu Konishi of shindo-jinen-ryu, and a young Gogen Yamaguchi of goju-ryu. Most of these men were founders of their own styles, and as such automatically became the highest rank that their agreed-on respective standards allowed."
http://www.judoinfo.com/karateranks.htm