The discovery in 1846 of the planet Neptune was a dramatic and spectacular achievement of mathematical astronomy. The very existence of this new member of the solar system, and its exact location, were demonstrated with pencil and paper; there was left to observers only the routine task of pointing their telescopes at the spot the mathematicians had marked.
Source: J. R. Newman (ed.) The World of Mathematics, New York: Simon and Schuster, 1956.
Contributed by: Zaady