If you have a spare twenty-five minutes, you should take the time to listen to the new Radiolab short: ≤ kg. Using the kilogram, the last measurement that uses a physical object, it explores the history of how we got exact measuring units from the French Revolution. And how those are changing into complex ideas.
There is also a brief visit to the Musée des Arts et Métiers (french website) to visit objects of measuring past. All in all, a great podcast from radiolab and well worth a listen!