Koichi Tohei (20 January 1920 – 19 May 2011) was a first one to be promoted to a 10 Dan by the Morihei Ueshiba ever. He taught people like Hiroshi Tada, Seigo Yamaguchi, Mitsugi Saotome, Sadateru Arikawa, Kazuo Chiba, Yoshimitsu Yamada, Steven Seagal and many others.
Mokuso is a Japanese term for silent meditation. The first kanji reads as “Moku” and means silence or stop and the second one is “So” and means to think or focus. Mokuso is a common way to start and to end a training session in the Japanese Martial Arts and especially Aikido.