As an interesting aside, back in the 80's I played at a club where one group played for very high stakes. A player chipped from off the green and the ball hung just on the lip of the hole. He walked up, looked at it, then went over to his cart to get his putter, probably 30 yards away. While he was walking back to finish, the ball fell. After the round the head pro called the USGA for a ruling. They held that the player was entitled to play his next stroke with his putter, so his actions were reasonable and the ball was holed without penalty.