Ancient Egyptians used wet sand to drag massive pyramid stones,

Wall painting from the tomb of Djehutihotep. Wall painting from the tomb of Djehutihotep. A large statue is being transported by sledge. A person standing on the front of the sledge wets the sand.

one question that long puzzled me is how Egyptians managed to move those colossal pyramid stones – some of which weigh several tons.

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.the stones were dragged over wet sand
Experiments have demonstrated that the correct amount of dampness in the sand halves the pulling force required.

"When the sand was dry, a heap of sand formed in front of the sled, hindering its movement; a relatively high force was needed for the sled to reach a steady state. Adding water made the sand more rigid, and the heaps decreased in size until no heap formed in front of the moving sled and therefore a lower applied force was needed to reach a steady state

The setup in the lab.
The picture on the right was taken while sliding over normalized sand wetted with 5% water. In the dry sand, a heap clearly builds up in front of the sled