From Troyat’s biography:
He sent for a theological student from Moscow to teach him the rudiments of the language. From the first day, the forty-two-year-old pupil threw himself into Greek grammar with a passion, pored over dictionaries, drew up vocabularies, tackled the great authors. In spite of his headaches, he learned quickly. In a few weeks he had outdistanced his teacher. He sight-translated Xenophon, reveled in Homer, discovered Plato and said the originals were like “spring-water that sets the teeth on edge, full of sunlight and impurities and dust-motes that make it seem even more pure and fresh,” while translations of the same texts were as tasteless as “boiled, distilled water.”
Sometimes he dreamed in Greek at night. He imagined himself living in Athens; as he tramped through the snow of Yasnaya Polyana, sinking in up to his calves, his head was filled with sun, marble and geometry. Watching him changing overnight into a Greek, his wife was torn between admiration and alarm. “There is clearly nothing in the world that interests him more or gives him greater pleasure than to learn a new Greek word or puzzle out some expression he has not met before,” she complained. “I have questioned several people, some of whom have taken their degree at the university. To hear them talk, Lyovochka has made unbelievable progress in Greek.” He himself felt rejuvenated by this diet of ancient wisdom. “Now I firmly believe,” he said to Fet, “that I shall write no more gossipy twaddle of the War and Peace type.”
Hat tip: languagehat.