A stream originating in Nevado Mismi, a mountain in southern Peru, is said to be the exact source of the Amazon river, the National Geographic Society reported. Global Positioning System (gps) equipment was used by a five-nation expedition to take measurements. The countries that participated in the expedition included the us, Poland, Peru, Canada and Spain. "The source of the Amazon could be defined as the most distant point in the drainage basin from which surface water runs the year around, or the furthest point from which water could possibly flow to the Atlantic,' says Andrew Johnson, geographer at the Washington-based Smithsonian Institute. "Nevado Mismi fits both the definitions,' Johnson added. The source of the Amazon has been a riddle for centuries. The Amazon springs from the Andes' glacial regions. "The trip's result is a highly reliable map of the Amazon's headwaters and a accurate determination of the river's source,' said Andrew Pietowski, who led the expedition.