King Coal by Upton Sinclair

Hal told himself with satisfaction that he was now to do the real work of coal-mining. His imagination had been occupied with it for a long time; but as so often happens in the life of man, the first contact with reality killed the results of many years' imagining. It killed all imagining, in fact; Hal found that his entire stock of energy, both mental and physical, was consumed in enduring torment. If anyone had told him the horror of attempting to work in a room five feet high, he would not have believed it. It was like some of the dreadful devices of torture which one saw in European castles, the "iron maiden" and the "spiked collar. " Hal's back burned as if hot irons were being run up and down it; every separate joint and muscle cried aloud. It seemed as if he could never learn the lesson of the jagged ceiling above his head -- he bumped it and continued to bump it, until his scalp was a mass of cuts and bruises, and his head ached till he was nearly blind, and he would have to throw himself flat on the ground.

Then old Mike Sikoria would grin. "I know. Like green mule! Some day get tough!"