Dive Brief:

• It seems that modern research has caught up with something the builders of the Egyptian pyramids long understood – mixing sand and water.
• What the modern researchers have been able to demonstrate is that the correct amount of water will create bridges between sand grains and sort of glues them in place, making it easier to pull stone-bearing sleds because the grains are not plowed up in front of the sled. 
• Pour too much water, however, and the structure falls apart and the friction goes back up.

Dive Insight:

The researchers figure that the difference between hauling stones as large as 2.5 tons over dry sand and properly wetted sand is being able to use half as many people. In hindsight, the explanation was there in a tomb painting that shows a statute being pulled on a sled over the sand as a figure pours water in front of it.