> He slept for only 4 hours a day

Edison as well. Interesting that.

When I was a teen, I was introduced to a friend of my step-father's that had the same affliction — he slept only 3 or 4 hours a day. He had told me it was unusual. I don't know how unusual it is. If it is common enough then von Neumann and Edison having the same inclination is of no significance.