In fact, having spent eight hours in physical labour,—half a day,—which formerly I used to spend in endeavouring to struggle with dulness, there still remained for me eight hours, out of which in my circumstances I required five for mental labour; and if I, a very prolific writer, who had been doing nothing but write during forty years, and who had written three hundred printed sheets, then if during these forty years I had been doing ordinary work along with working-people, and, not taking into consideration winter evenings and holidays, had been reading and learning during the five hours a day, and had written only on holidays two pages a day (and I have sometimes written sixteen pages a day), I should have written the same three hundred printed sheets in fourteen years.
— from What Shall We Do? by Tolstoy, Leo, graf