I worked with John Wiegley for a couple of years and discovered one of his projects, Ledger (https://ledger-cli.org/ https://ledger-cli.org/), during our conver

I worked with John Wiegley for a couple of years and discovered one of his projects, Ledger (https://ledger-cli.org/ https://ledger-cli.org/), during our conversations. This tool taught me double-entry accounting and helped me understand finance and blockchains on a deeper level. Unfortunately, I’m too lazy to use the tool on a daily basis, so it’s the second most insightful piece of software I’ve never used :D