In 1908, the incomparable Harry Houdini obligingly posed in front of our letterbox repository before jumping into the freezing Charles River, fully manacled. In the century which followed, the hard-drinking engineers of MIT precisely and in the most scientific manner mapped the unique global coordinate of our repository, as the name indicates. Our stamp for this box is a lighthouse, as the repository is astride a navigation beacon. Lastly, a caveat: because of indifferent pedestrian traffic (with nosy non-letterboxers who might not respect the great tradition), we had to put Smoot-165 in a place totally inaccessible to Charles River lubbers, but, at 6' off the "ground" on the second eastward pylon, still within reach to many thousands of Charles River lovers.