The Wind in the Willows - Kenneth Grahame

The Rat pushed the paper away from him wearily, but the discreet Mole took
occasion to leave the room, and when he peeped in again some time later, the
Rat was absorbed and deaf to the world; alternately scribbling and sucking the
top of his pencil. It is true that he sucked a good deal more than he scribbled; but
it was joy to the Mole to know that the cure had at least begun.