This image may have been reflected from some part of the room where the gazer had not noticed it, and may have been either before or behind the operator. The magnifying-glass would naturally make the small, condensed letters legible, as a play-bill would be many times larger than a crystal ball, and its minute image naturally too small to read, being reduced by the circular surface. Usually, however, the image is not on the surface of the crystal, but in the beholder’s eye; therefore when this image appears more clearly under magnification, the result is due to the expectation of the gazer based upon his experience of an invariable rule. This acts as a stimulus upon the visual function, which must be in an exceedingly sensitive state to produce visions at all. When, however, no result or a negative result follows the use of the glass, then we can safely assume that the gazer was naturally of a critical turn of mind, and was disposed to distrust sensual impressions; hence the glass became a disturbing influence, interfering with or even completely obliterating the eye-picture. Many attempts have been made to establish distinctions between the different materials used for crystals, proceeding on the theory that subtle emanations from them affected the gazer and played an important part in producing the desired vision. That the beryl produced a greater number of these visions than any other mineral was the old belief which is still upheld in some quarters to-day; one scryer, indeed, asserts that his clearest and most satisfactory visions were seen in a cube of blue beryl, the beautiful color appearing to dispose the soul to a harmonious unfolding of its latent aptitudes.[314] Among the instructions given to a would-be crystal gazer, the question of a proper and wholesome diet is not overlooked, as anything which tends to disturb the serenity of the organism will also interfere with the due exercise of the special clairvoyant faculty that expresses itself in crystal visions. A curious special recommendation made by one of the exponents of the art is that good results can be had by drinking an infusion of mugwort (_Artemisia vulgaris_), or of chicory (_Cichorium intybus_), because of their tonic and antibilious qualities. Moreover, we are told that these herbs are under the influence of the zodiacal sign Libra, the sign controlling the virtues of the beryl.[315] Above all the portion of the lunar month when the moon is on the increase is said to be far the best season for scrying, as the old astrologers recognized an affinity between the moon and rock-crystal.