When trolling around looking for a likely restaurant in which to eat, we tend not to pay too much attention to the décor, the design, the number of persons eating there, or whatever testimonials decorate the front windows. We just want to look at the menu — the true soul of any restaurant and the one thing that will perpetuate its memory long after its doors have closed. And though not widely known, one of the country’s greatest repositories of menus is at the New York Public Library. Chow’s latest “Obsessives” video introduces us to librarian Rebecca Federman and the collection she oversees. When did ramps first start appearing? And why did restaurants ever stop using gigantic, Art Nouveau titles and engraved portly figures? We’re nostalgic already.