Wilkie Collins book The Woman in White
Source: Collins explaining what he calls the literary principal guiding him, in the preface of the second edition of The Woman in White. Also in Reality's Dark Light: The Sensational Wilkie Collins by Maria K. Bachman & Don Richard Cox [University of Tennessee Press, 2003, ISBN 1-572-33274-3] ( p. xiv https://books.google.com/books?id=_X8AlmIp0dwC&pg=PR14)