In 1821, German mathematician Carl Friedrich Gauss invented the heliotrope, a device that utilizes a mirror to reflect sunlight over a distance to mark survey points. Heliotropes were commonly used in surveying until the 1980s when GPS technology replaced long-distance surveying.
Gauss was known for many things relating to mathematics in his time, and he was sometimes referred to as the "Princeps mathematicorum" or the "Prince of Mathematicians." The Gauss Prize, one of the highest honors in mathematics, was named for him, as well as Gauss's Law and Gauss's law for magnetism. His face adorns the 10 Deutsche Mark banknote and a 1977 East German postage stamp.