Cyanometer Postcard

A cyanometer is a tool that lets you grade the blueness of your sky, invented in 1789 by Horace Bénédict de Saussure.

This genius modern version is combined with a postcard! Simply hold up to the sky, look through the hole and then on the back write the time & shade number. Pop in the post to a friend.

Simple brilliance by Macarena Ruiz-Tagle.