The most famous spring is Cleopatra's Bath, which has crystal-clear natural spring water that gurgles up into a large stone pool, and is a popular bathing spot for locals.

BBC: Siwa: An Egyptian oasis

He manufactures every component of his watches himself, except for the main spring and sapphire crystal.

FORBES: Magazine Article

Friend vibrates a lead zirconate titanate crystal, and those vibrations twist a spring-like element attached to a rotor.

FORBES: Breakthroughs