The 'Sympathique' clock

In a letter to his son dated 26 June 1795, the maker of this clock, Breguet (1747-1823), described its purpose: 'I have invented a means of setting a watch to time, and regulating it, without anyone having to do it… This is how it works: you have a second clock or a marine arranged to receive the watch ... every night on going to bed, you put the watch into the clock. In the morning, or one hour later, it will be exactly to time with the clock. It is not even necessary to open the watch'. 

Built into the watch is motion work which automatically sets the hands to the clock's time, as well as correcting the watch's regulator by any degree of inaccuracy registered at the moment of synchronisation.  The term 'sympathique' was chosen by Breguet to express the notion of harmony and concord achieved in this.  The timepiece was made for George IV in 1814 and the watch appears to have been worn regularly by him.