Peter Henlein a locksmith from Nuremberg, Germany has been given credit for inventing the spring powered clock in 1510. His compact, portable clock was a major advance for timekeeping. The balance spring that he used in the clock improved the accuracy of he clock. His invention would lead to even smaller clocks like the pocket watch and the wrist watch. Henlein was the first maker of the pocket watch, which could run up to 40 hours between windings.
Information on Clocks:
Image of Henlein showing his watch