rigorously

Before daybreak he would awake, leave the inn after rigorously paying his bill, and reaching the forest, he would, under pretence of making studies in painting, test the hospitality of some peasants, procure himself the dress of a woodcutter and a hatchet, casting off the lion’s skin to assume that of the woodman; then, with his hands covered with dirt, his hair darkened by means of a leaden comb, his complexion embrowned with a preparation for which one of his old comrades had given him the recipe, he intended, by following the wooded districts, to reach the nearest frontier, walking by night and sleeping in the day in the forests and quarries, and only entering inhabited regions to buy a loaf from time to time.

Researchers discovered that these drivers possess remarkably enlarged hippocampi, a testament to the brain's profound neuroplasticity when rigorously challenged.