Ancient Egyptians transported pyramid stones over wet sand

"Physicists from the FOM Foundation and the University of Amsterdam have discovered that the ancient Egyptians used a clever trick to make it easier to transport heavy pyramid stones by sledge. The Egyptians moistened the sand over which the sledge moved. By using the right quantity of water they could halve the number of workers needed. The researchers published this discovery online on 29 April 2014 in Physical Review Letters."