Peter Goldsbury

In Shinto mythology, Ame no Torifune was a deity, in fact a boat, used by the other deities for transportation between the high plain of heaven and the land of reed plains (i.e., Japan). Morihei Ueshiba was steeped in Shinto, as interpreted by the Omoto religion, and used this exercise as a form of purification, called misogi. The exercise is followed by an exercise called furitama, shaking the ball, which was originally believed to be a form of inducing divine possession, called chinkon kishin. As Robin stated, the rowing exercise is also called funa kogi undo and all my teachers followed Ueshiba's example by doing this exercise at the very beginning of a training session.