[Sangetsu]

Calligraphy. When I studied kendo, all students had to read Musashi's go-rin-no-sho, in which he writes about the proper way of the sword being a combined way of the pen and the sword.

If you look at the writing of the great martial arts masters, you'll usually notice that they have a striking way of writing.

Calligraphy is mental and physical, it requires great focus and coordination. It is described as the "7th martial art".