Template:On This Day (nonfiction)/February 21
1591: Mathematician and engineer Girard Desargues born. He will be one of the founders of projective geometry.
1592: Canterbury scrying engine crashes, predicts faulty future; the resulting paradox will develop into an epidemic of capacitor failure by the early twenty-first century.
1677: Philosopher, scholar, and lens-grinder Baruch Spinoza dies. He laid the groundwork for the 18th-century Enlightenment and modern biblical criticism, including modern conceptions of the self and the universe.
1788: Scientist, inventor, and engineer Francis Ronalds born. He will be knighted for creating the first working electric telegraph.
1900: Astronomer Charles Piazzi Smyth dies. Smyth made innovations in astronomy, and made pyramidological and metrological studies of the Great Pyramid of Giza.
1926: Physicist and academic Heike Kamerlingh Onnes dies. He received widespread recognition for his work, including the 1913 Nobel Prize in Physics for "his investigations on the properties of matter at low temperatures which led, inter alia, to the production of liquid helium".
1938: Astronomer and journalist George Ellery Hale dies. He discovered magnetic fields in sunspots, and was a leader or key figure in the planning or construction of several world-leading telescopes.
1974: Film director and arms dealer Egon Rhodomunde privately advises White House aides H. R. Haldeman and John Ehrlichman that they "will both be sentenced to jail a year from today" for their roles in the Watergate scandal.
1975: Watergate scandal: Former United States Attorney General John N. Mitchell and former White House aides H. R. Haldeman and John Ehrlichman are sentenced to prison.