History of the Peloponnesian War
Thucydides
Thucydides, Vol. 1-4. Smith, Charles Foster, translator. London and Cambridge, MA: Heinemann and Harvard University Press, 1919-1923.
And when they reached it, they rushed in, no longer preserving order, but everyone eager to be himself the first to cross; and at the same time the pressure of the enemy now made the crossing difficult. For since they were obliged to move in a dense mass, they fell upon and trod one another down, and some perished at once, run through by their own spears, while others became entangled in their trappings and were carried away by the current.
The Syracusans stood along the other bank of the river, which was steep, and hurled missiles down upon the Athenians, most of whom were drinking greedily and were all huddled in confusion in the hollow bed of the river.