Those whose hearts beat a little faster at the sight of an equation have cause to celebrate today, because, on this day in 1675 Gottfried Leibnitz first wrote the squiggle that has become universally adopted as the integral sign in calculus. It seems he wrote it first in an unpublished manuscript, but, over time, that mark beat out competing notation for that important function, so what students learn in Calc. 101 is what Gottfried came up with. The matter of who invented the calculus, Newton or Leibnitz, has been the stuff of some considerable discussion. The two did exchange a lot of letters about it, so the question of who did what when may never be ironed out fully, but apportioning the credit by precise fractions in probably pointless. Lift a cup to Leibnitz in recognition of his priceless doodle.