In 1642 Blaise Pascal developed a calculating machine to lighten the workload for his father, a tax official in Normandy. For the first time, a machine added and subtracted sums automatically by means of an ingenious little part: the sautoir. The "Pascaline" was built to simplify business calculations. Its wheels had a varying number of teeth: 10 to calculate toises and livres (contemporary units of measurement and currency, respectively), 20 to count sols (there were 20 sols to a livre), 12 for deniers (12 deniers to a sol) and so on. Only nine of the machines have survived. This one, dated 20 May 1652, is similar to the machine Pascal sent in June of the same year to Sweden's Queen Christina, a great collector of art works and scientific objects.