Template:Selected anniversaries/October 16
1584: Famed illustration Leonardo Draws Clock Head is "a reasonably accurate depiction of events as I remember them", says artist, inventor, and math detective Leonardo da Vinci.
1655: Physician, mathematician, and theorist Joseph Solomon Delmedigo dies. His Elim (Palms) deals with astronomy, physics, mathematics, medicine, metaphysics, and music theory.
1797: Carl Friedrich Gauss records in his diary that he has discovered a new proof of the Pythagorean Theorem.
1843: Sir William Rowan Hamilton comes up with the idea of quaternions, a non-commutative extension of complex numbers.
1868: Physicist and crime-fighter Gustav Kirchhoff uses the emission of black-body radiation by heated objects to detect and prevent crimes against physical constants.