"Monsieur Des Cartes slept much, or at least his awakening was never forced; so soon as ever he perceived himself dis-ingaged from sleep, he studied, meditating in Bed, and raised but half his Body now and then, to commit his thoughts to writing. This is the reason why he often continued ten Hours, nay, sometimes twelve in his Bed."

(Adrien Baillet, Life of Monsieur Des Cartes, 1693)