JF Ptak Science Books Quick Post
This thinking stick comes to us via the courtesy of the Scientific American Supplement (19 August 1876, page 542), and shows a lovely Victorian non-SteamPunk answer to on-the-run calculation. It is an almost-elegant device, and seems as though it should work just fine. Its utility as a writing instrument seems a bit limited, as seems the calculator part, but the whole of it seems to be full of possibility–and a very nice piece of dedicated thinking.
[Text describing the invention below.]
Other nice examples of adding/writing found in the U.S. Patent Office via GooglePatents are seen below: