A crystal ball, also known as an orbuculum or crystal sphere, is a crystal or glass ball and common fortune-telling object. It is generally associated with the performance of clairvoyance and scrying in particular. In more recent times, the crystal ball has been used for creative photography with the term lensball commonly used to describe a crystal ball used as a photography prop. History In the first century CE, Pliny the Elder describes use of crystal balls by soothsayers ("crystallum orbis", later written in Medieval Latin by scribes as orbuculum). By the fifth century CE, scrying was widespread within the Roman Empire and was condemned by the early medieval Christian Church as heretical. Dr. John Dee was a noted British mathematician, astronomer, astrologer, geographer, and consultant to Queen Elizabeth I. He devoted much of his life to alchemy, divination, and Hermetic philosophy, of which the use of crystal balls was often included. Crystal gazing was a popular pastime in the Victorian era, and was claimed to work best when the Sun is at its northernmost declination. Immediately before the appearance of a vision, the ball was said to mist up from within. Romani fortune tellers used crystal balls to predict the fortune of their customers. Art of scrying The art or process of "seeing" is known as "scrying", whereby images are claimed to be seen in crystals, or other media such as water, and are interpreted as meaningful information. The "information" gleaned then is used to make important decisions in one's life (i.e. love, marriage, finances, travel, business, etc.). When the technique of scrying is used with crystals, or any transparent body, it is known as crystallomancy or crystal gazing. In stage magic Crystal balls are popular props used in mentalism acts by stage magicians. Such routines, in which the performer answers audience questions by means of various ruses, are known as crystal gazing acts. One of the most famous performers of the 20th century, Claude Alexander, was often billed as "Alexander the Crystal Seer". Properties A crystal ball is essentially a bi-convex spherical lens with a uniform radius of curvature, although without its edges and center material truncated as in a conventional lens construction. Thus the principles of optics may be applied to analyze its imaging characteristics. As a lens, a transparent sphere of any material with refractive index greater than one bends rays of light to a focal