The Spirits' Book
Book Two - The Spirit World
Chapter VIII - Emancipation of the Soul
449. Does second sight occur spontaneously, or through the will of those who possess that gift?
“It generally occurs spontaneously, but will often plays an important role in producing this phenomenon. Look at fortune-tellers, for example, and others who really have that power, and you will find that their will helps them with this second sight or what you call vision.”