We [Einstein and Ernst Straus] had finished the preparation of a paper and were looking for a paper clip. After opening a lot of drawers we finally found one which turned out to be too badly bent for use. So we were looking for a tool to straighten it. Opening a lot more drawers we came upon a whole box of unused paper clips. Einstein immediately started to shape one of them into a tool to straighten the bent one. When asked what he was doing, he said, ‘Once I am set on a goal, it becomes difficult to deflect me.’

— Ernst Straus, “Memoir,” in A.P. French, ed., Einstein: A Centenary Volume, 1979

(Einstein said to an assistant at Princeton that this was the most characteristic anecdote that could be told of him.)