In Aiki News 76, Tenryu gives his account when he met Ueshiba.
But, that issue also has Ueshiba talking about what happened.
Aiki News Issue 76 - Ueshiba wrote:
Ueshiba: Tenryu was laughing then. He was over six feet tall and weighed something over 240 pounds. I was such a small man it was impossible to have a sumo match with him. In any event, I told him to have a try. I grabbed his hand lightly. then I told him to push me back hard. Although he was pushing me with all his might I said to him, "You don't have much power, do you?". Then I moved slightly and he fell. I was sitting the whole time.