“The hard sphere,” declared the British physicist, Sir James Jeans, “has always a definite position in space; the electron apparently has not. A hard sphere takes up a very definite amount of room, an electron—well, it is probably as meaningless to discuss how much room an electron takes up as it is to discuss how much room a fear, an anxiety, or an uncertainty takes up.”
from The Universe and Dr. Einstein by Lincoln Barnett, c. 1948, Time, Inc.