In 1639, the first known observations and recording of a transit of Venus were made.
The observations were made by the English astronomers Jeremiah Horrocks and William Crabtree. Horrocks was able to make three measurements and calculate for Venus its transit path, angular size, and orbital velocity. Based on his calculations, he concluded that the Sun was further away from the Earth than previously thought.
Learn more at http://www.transit-of-venus.org.uk/history.htm.