Analytical Engine emulator in Raku
In the early 1800s, the English mathmatician Charles Babbage designed (but sadly never built) a mechanical general-purpose computer. Unlike previous inventions which were designed to perform a single task, the Analytical Engine was designed such that it could perform many tasks, and is therefore often considered to be the 'first' computer.
There are many excellent sites, such as jfinkels' GitHub and John Walker's site which give great introductions to the workings of the proposed device.