An Italian engineer thinks he has cracked the mystery of the Incan counting system. If he is correct, this is a fiendishly clever system. It is based on the Fibbonacci series, such that there is an area on the counting pad representing 1, 2, 3, 5, and then 10, 100, 1000, etc. At any point, you can simplify the representation by combining two counters into one in a higher region of the units section, or 10 into one in the logarithmic portion around the edge. The slide show on the page shows how that is done, by adding 9 and 7. Some are disputing whether this is the correct interpretation of what these artifacts do based on the historical evidence from writings of the last days of the Inca, but it is an elegant solution whether the actual one the Incas used or not.