About 12 years ago I met a 40-year-old 6-dan teacher in Taiwan. He was quite small, even for a Chinese. He reminded me quite a lot of Akira Tohei sensei because of his small size.
Being my usual fanatical self, I immediately asked to be his uke during class. When I got the chance, I was surprised by how easily he moved and yet how he seemed to be always full of power, even though he usually moved slowly in order to teach. And yet, when one looked at him, he seemed quite normal. There was nothing to indicate how powerful he really was. Only after I was his uke, did I find out.
Afterwards, I sat down next to my Taiwanese friend and with wide-opened eyes, I told him how I felt. He said, "Yes. Wong sensei's cup is full."