In the modern Western world, group activities like these are mainly just a lazy punchline for movies (and/or a source for rap-metal band names), but different cultures have had wildly different understandings of the act. At one extreme, there are certain remote tribes in sub-Saharan Africa that had — until recently — never encountered this form of self-pleasure, and find the idea of it completely bizarre (see a study here); at the other, you have civilizations like Ancient Egypt, which thought of the act as literally sacred (via MEL).

This was actually embedded into the mythology of Ancient Egypt: The very first god, Atum, was said to have initiated creation by using his “seed” to produce the gods Shu and Tefnut (via Victor H. Matthews and Don C. Benjamin). Given this understanding, it should be no surprise that the act was understood as a life-giving one that symbolized the fertility the Nile would bring when it flooded every summer.

As such, an ancient ritual was performed once a year by the Egyptian Pharaoh, who would walk down to the shore, strip naked, and ceremonially pleasure himself over the water. Once he finished, all the other men would follow suit (via Face2Face Africa). Then, presumably, they would all spend the remainder of the year struggling to look each other in the eye.