The Righteous Mind by Jonathan Haidt — Read

In September 1941, William McNeill was drafted into the U.S. Army. He spent several months in basic training, which consisted mostly of marching around the drill field in close formation with a few dozen other men. At first McNeill thought the marching was just a way to pass the time, because his base had no weapons with which to train. But after a few weeks, when his unit began to synchronize well, he began to experience an altered state of consciousness:

Words are inadequate to describe the emotion aroused by the prolonged movement in unison that drilling involved. A sense of pervasive well-being is what I recall; more specifically, a strange sense of personal enlargement; a sort of swelling out, becoming bigger than life, thanks to participation in collective ritual.1