Letters 94.63

Already he has joined many kingdoms into one kingdom; already Greeks and Persians fear the same lord; already nations Darius had left free submit to the yoke: yet he passes beyond the Ocean and the Sun, deeming it shame that he should shift his course of victory from the paths which Hercules and Bacchus had trod; he threatens violence to Nature herself. He does not wish to go; but he cannot stay; he is like a weight that falls headlong, its course ending only when it lies motionless.

Seneca, Letters to Lucilius 94.63, translated by Richard Mott Gummere