This isn't Ueshiba, but it does reference push tests.
From Westbrook and Ratti's Aikido and the Dynamic Sphere
This is just a small excerpt. There is a page or so going over push tests.
Westbrook and Ratti wrote:
He will push and you will neutralize his power as if you were a rock against which his power was being discharged. In advanced stages of the art, you should be able to rechannel the force he is trying to use against you, and even be able to push back several men as they strain against you to no avail.