Mark Twain and his habits
Few people know that Mark Twain wrote poems and tales for children, he's more likely famous for his ingenious "Answers to Correspondents" (his comments on the readers' letters were published as a separate book). Twain is also known for great aphorisms, which eloquently demonstrate his attitude to work: "Whoever has lived long enough to find out what life is, knows how deep a debt of gratitude we owe to Adam, the first great benefactor of our race. He brought death into the world."
He used to come to his library right after breakfast standing there till the evening meal. As he missed lunch, and no one from his family dared to disturb him - they totted the horn in case of need - he usually could work without breaks for several hours straight. After supper Twain was reading out his fresh written works to the whole family. He was pleased to have listeners and almost always his evening performances got over the footlights.
Twain didn't work on Sundays, spending weekends with wife and children, reading and sleeping in the daytime somewhere in shady place near the house.
It's worthy of note that whether he was working or not, he always smoked cigars.