I asked her whether she had ever taken opium, as the description given of its effects in “Villette” was so exactly like what I had experienced, —vivid and exaggerated presence of objects, of which the outlines were indistinct, or lost in golden mist, &c. She replied, that she had never, to her knowledge, taken a grain of it in any shape, but that she had followed the process she always adopted when she had to describe anything which had not fallen within her own experience; she had thought intently on it for many and many a night before falling to sleep,—wondering what it was like or how it would be,—till at length, sometimes after the progress of her story had been arrested at this one point for weeks, she wakened up in the morning with all clear before her, as if she had in reality gone through the experience, and then could describe it, word for word, as it had happened. I cannot account for this psychologically; I only am sure that it was so, because she said it.
Elizabeth Gaskell, The Life of Charlotte Brontë, ed. by Anne Taranto (New York: Barnes & Noble Classics, 2005; 1857), p. 507.