A painting in the tomb of Djehutihotep (El-Bersheh, Egypt, c. 1850 BC) shows 172 men hauling a colossal statue on a wooden sledge while one man pours water onto the sand in front of it. It was long read as a ritual act.

• ✓doi.org

This man isn't performing a ritual. He's doing physics. This scene comes from an Egyptian tomb almost 4,000 years old. A hundred and seventy-two men drag a giant stone statue on a wooden sledge. And at the front, one man pours water onto the sand. For a long time, many read that as a ritual act. Then in 2014, physicists in Amsterdam put it to the test. On dry sand, a sledge pushes up a heap in front of it. Dampen the sand just right, and water holds the grains together. The pull needed dropped by about half. Too much, and it turns to sludge. So that one jar may have done the work of half the crew.