There is a cool documentary about how Einstein was trying to prove relativity theory, and it involved a lot of work, special telescope, traveling, war... I think it was done at third attempt. Imagine if he would have died before proving it ... My point is, he didn't stop in the theory, but also designed an experiment and worked a lot to get it proved. Cajal's statement clearly doesn't apply to him. I'll try to find the video, or if someone remembers please link it.