The first transit circle was created by the Danish astronomer Ole Christensen Römer (1644-1710) known especially for having demonstrated in 1675, when he was an assistant at the Paris Observatory and a member of the Academy of Science, that light has a finite speed, thus contradicting the fundamental postulate of Cartesian physics of the instantaneous propagation of luminous signals. But the transit circle was built by Römer in 1704 when he was the director of the Copenhagen observatory; he had left the Paris observatory in 1681 after working there as assistant to Jean Picard (1620-1682) and contributing decisively to making it the most important in Europe, together with the Greenwich Observatory.