Biggest acorns ever

The giant mutant acorns I saw are apparently from a bur (or burr) oak, Quercus macrocarpa. I'll bring one to the office to show you. Web images are mostly lacking in scale—I had to look for about half an hour before finding the image that clinched the identification. I'll check the leaves tomorrow too, if I can do so without incurring the wrath of the guards of the Bethesda Naval Hospital, where the tree is.