If you are interested in non-electronic digital computers you might want to check out this previous discussion:(https://news.ycombinator.com/item?id=7824588)

If you are particularly interested in domino logic and adders, baddox posted this video (https://www.youtube.com/watch?v=SudixyugiX4), petercooper posted this one (https://www.youtube.com/watch?v=lNuPy-r1GuQ) by Matt Parker (the same guy in this video) and I documented a 2-bit build I did (http://imgur.com/a/qq7Kl).