"The study was done by Christian Wagner and colleagues at Saarland University in Germany, along with researchers in the Netherlands, Iran and France. The team was inspired by an ancient Egyptian wall painting showing a huge statue being hauled across the sand on a sledge in about 1800 BC. The painting has a detail that has long puzzled Egyptologists: a worker who appears to be pouring water onto the sand in front of the sledge while others appear to be carrying water to replenish his supply."