How to Read the Crystal is one of several occult treatises written by Walter Gorn Old (1864-1929), the pseudonym of Walter Richard Old who also wrote under the name, Sepharial.
Old is best known for his works on using astrology to predict events on the stock market and horse racing.
In How to Read the Crystal, Old attempts to teach the reader how to use any type of reflective device such as a crystal ball, mirror, or dish of water to divine the past, present, and future.
In essence, he is teaching self-hypnotism where the viewer sees symbols within the reflective surface that are subjectively interpreted. In the process, he relates stories and experiences of seers and also advertises the best places to buy crystal balls.
The author is also kind enough to extend a warning to the new student about symptoms which they may experience as they indulge in reading the crystal ball:
Loss of memory, hysteria, absentmindedness, unconscious utterance of one's thoughts, illusions and hallucinations, irritability, indifference to one's surroundings, and similar perversions, are among the products of the newly-evolved psychic faculty.
This book is NOT recommended for those who do not know what they are attempting to do.