Have you ever wondered how blue the sky is? Over two hundred and thirty years ago a young Swiss physicist named Horace-Bénédict de Saussure was thinking the very same thing. He invented a rather simple gage that consisted of 52 different hues of blue arranged from light to dark on a gradated circular scale. His device, called a cyanometer, helped to confirm that the sky’s colour changed with the elevation. The bluest blue Saussure recorded was atop Mont Blanc, registering at the 39th degree of intensity. Later in 1802, German explorer and scientist Alexander von Humboldt discovered the deepest blue, the 46th degree of intensity, while atop the Andean mountain Chimborazo. Over time, the cyanometer failed to provide much valuable information to the scientific community and eventually fell out of favour.