For a man who wrote only three hours a day, Anthony Trollope was quite productive. He churned out 250 words every 15 minutes—meaning by the time he was done working each day, he had produced 3000 words. And if he finished the book he was working on before his daily time allotment was up, he wouldn’t stop writing. Instead, he’d immediately begin another book.
Found at Mental Floss. The article also contains information about writing habits of Poe, , Lewis Carroll, and Virginia Woolf.