Ah, from the front page of Aikido Journal, comes this article. Seems Ueshiba kept having people push and pull him into his older years.
Aiki News Issue 99 - Interview with Takafumi Takeno wrote:
That was only shortly after I had begun practicing aikido so I didn't really understand the high level of what O-Sensei was demonstrating. I remember that he told his students to push and pull him, but try as they might he remained unmoved, impervious to their efforts.
So, why is it, that something as fundamental as this ... something Ueshiba did most of his martial career (after training with Takeda, it seems) ... that this hasn't spread throughout the aikido world?