Rømer's demonstration that light has a finite speed

As early as in 1676, the Danish astronomer Ole Rømer proposed an experiment to measure the time light takes in propagate from the Sun to the Earth. In 1738 Voltaire published The Elements of Sir Isaac Newton's Philosophy; in that book Voltaire provides this beautiful illustration of Rømer's demonstration. The conclusion was that "light employs seven or eight minutes in its passage from the Sun to the Earth".