In the world of modern portable devices, it may be hard to believe that merely a few decades ago the most convenient way to keep track of time was a mechanical watch. Unlike their quartz and smart siblings, mechanical watches can run without using any batteries or other electronic components.
https://ciechanow.ski/mechanical-watch/
https://blog.adafruit.com/2022/07/19/how-a-mechanical-watch-is-made-bciechanowski/