What combination of circumstances brought forth each prediction we do not know. The original coincidences have been lost and all that remains are the series of intricate tabulations and data, as curious and as arbitrary as the signs read on tea leaves, or the fortunes ascribed to numbers.
Each planet was the indicator of certain diseases, most of which are associated with the part of the body of which that planet was ruler. When a planet was within fifteen degrees of the Sun, it was still within reach of its emanations, but when within twelve degrees it became burnt and useless. A planet was entirely devoid of power when its motion appeared to be retrograde. The Moon was powerless when in the Milky Way. The planets were at the height of their power in the fifth, seventh, tenth and eleventh houses. They were weak in the sixth, eighth and twelfth, but the ruler of those houses portended evil to all with whom he shared an aspect.
The houses of the heavens were allotted to specialities. The first belongs to the questioner or client, and the fourth to medicine, in which house a practitioner may read whether the medicine will be alleviating to the patient.
For casting the horoscope of the disease the Moon must be set to the place in the zodiac where it was at the hour of attack. The times of crises will come when the Moon is in quadrature or opposition, and the intermediate symptomatic days can be found in a similar manner.
After finding the time of crises, the doctor must make out a map of the heavens:
"If you see the Moon hampered, everything contrary and unpropitious, you will decide that nature will succumb to disease."
That sounds like extraordinarily bad psychology, but:
"The contrary would be the case if the Moon was connected only with more favorable planets and fixed stars."
And what ill-omened illness cast the doctors in ill repute so that certain combinations would curse their business forever?
"When the map of the sky at the beginning of the disease has been set up, the seventh house must be examined carefully and if a malignant planet is located there, or if a planet there catches the emanations of a malignant planet, the ruler of the house will be unpropitious and as the ruler of the seventh house is the significator of the doctor, it is seen that he will suffer, so the patient will take care that the present doctor is discharged and another one found."
Was that restriction originally made so that the patient would have reason to dismiss a man whose bedside manner was disagreeable; just as the doctors were careful to add the following as an excuse for themselves?
"The times of distant crises are apt to change, not only because of the stars, as we have been hearing, but for other reasons, which are numbered as six by the doctors, as these lines show:
"'The times of crises are changed we're aware By causes, strength, symptoms, stars, medicine and care.'"
After all, the poor physicians had to have some way out if the unexpected happened.
The planets were not only represented by colors and flowers and parts of the body, but by metals as well.
"The bodies sevene eek, lo. hem heer anoon
Sol gold is, and Luna silver we threpe,
Mars yren, Mercuries quik-silver we clepe,
Saturnus leed, and Jupiter is tin,
And Venus coper by my fader kin!"
Thus Chaucer describes them in Chanoun Yemannes Tale, which is the story of an alchemist whose intentions were none too good. Alchemy was not always a device to fool the ignorant. It was a half-science, closely allied to astrology, and no more irrational. Just as the men and heavens were thought to be made in the same pattern so all metals were thought to have a common base, something a bit like the soul of quicksilver, but a more subtle quicksilver than was known, which when touched with something like sulphur, only a more philosophic sulphur, would produce any metal. The alchemists searched for this omnisolvent which would dissolve everything into this original soulful state (how they meant to keep it when they had it, if it would dissolve every kind of container they do not tell), and they sought the Philosopher's Stone, the elixir of life, not only to transmute the soul of quicksilver into gold, but to give mortals an indefinite span of years.
Such aims, if sincere, sound incredible, but they were no more absurd than the mythical Fountain of Youth which led Ponce de Leon to make his wonderful explorations in southeast America; and for the transmutation of metals there was a real basis.