Having read about the resentrecent foot traverse of Antarctica by Colin O'Brady I was wondering which means the polar explorers of former, pre-GPS times did useused to determine that they hathad reached the North or South Pole. Obviously, you cannot use a compass since it would guide you to magnetic north or south and not to the pole itself.
So what means havedid they been usinguse or (to make it a bit more open) could they have used?