A man is strolling past the mental hospital and suddenly remembers an important meeting. Unfortunately, his watch has stopped, and he cannot tell if he is late or not. Then, he notices a patient similarly strolling about within the hospital fence.
Calling out to the patient, the man says, “Pardon me, sir, but do you have the time?”
The patient calls back, “One moment!” and throws himself upon the ground, pulling out a short stick as he does. He pushes the stick into the ground, and, pulling out a carpenter’s level, assures himself that the stick is vertical.
With a compass, the patient locates north and with a steel ruler, measures the precise length of the shadow cast by the stick.