Su's clock tower also featured the earliest known endless power-transmitting chain drive in the world, as outlined in his horological treatise of 1092.
It took over three years, and the most advanced horological technique in engineering this truly one-of-a-kind timepiece; only one watch was ever built.
It took its special place last year on the sports watch scene, with its much-loved horological complication in the shape of a self-winding chronograph movement.
