I started learning the soroban (Japanese abacus) 2 years ago because I wanted to understand how people used it to perform calculation feats. I spent a year practicing using the abacus mechanics, and another year replacing the physical abacus with a mental abacus, so I can operate it all in my mind.

So here's some analysis of my progress. My results aren't impressive, but cultivating the mental abacus has been quite interesting!