Source: http://phys.org/news/2014-04-ancient-egy...

The Egyptians were probably aware of this handy trick. A wall painting in the tomb of Djehutihotep clearly shows a person standing on the front of the pulled sledge and pouring water over the sand just in front of it.

Besides revealing something about the ancient Egyptians, the results are also interesting for modern-day applications. We still do not fully understand the behaviour of granular material like sand. Granular materials are, however, very common. Other examples are asphalt, concrete and coal. The research results could therefore be useful for examining how to optimise the transport and processing of granular material, which at present accounts for about ten percent of the worldwide energy consumption.

Read more at: http://phys.org/news/2014-04-ancient-egyptians-pyramid-stones-sand.html#jCp