The Philosophy of Natural Magic, by Henry Cornelius Agrippa, L. W. de Laurence ed. , at sacred-texts.com
There is also a certain kind of divination by dreams which is confirmed by the traditions of philosophers, the authorities of divines, the examples of histories and by daily experience. By dreams I do not mean vain and idle imaginations, for they are useless and have no divination in them, but arise from the remains of watchings, and disturbance of the body. For, as the mind is taken up about and wearied with cares, it suggests itself to him that is asleep. I call that a true dream which is caused by the celestial influences in the phantastic spirit, mind or body, being all well disposed. The rule of interpreting these is found amongst astrologers, in that part which is wrote concerning questions: but yet that is not sufficient, because these kinds of dreams come by use to divers men after divers manners, and according to the divers qualities and dispositions of the phantastic spirit. Wherefore, there cannot be given one common rule to all for the interpretation of dreams. But, according to the doctrine of Synesius, seeing there are the same accidents to things, and like befalls like, so he which hath often fallen upon the same visible thing, hath assigned to himself the same opinion, passion, fortune, action, and event. As Aristotle saith, the memory is confirmed by sense, and by keeping in memory the same thing, knowledge is obtained; as also, by the knowledge of many experiences, by little and little, arts and sciences are thus obtained. After the same account you must conceive of dreams. Whence Synesius commands that every one should observe his dreams and their events, and such like rules, viz., to commit to memory all things that are seen, and accidents that befall, as well in sleep as in watching, and with a diligent observation
consider with himself the rules by which these are to be examined; for by this means shall a diviner be able, by little and little, to interpret his dreams, if so be nothing slip out of his memory. Now, dreams are more efficacious when the Moon overruns that Sign which was in the ninth number * of the nativity, or revolution of that year, † or in the ninth Sign from the Sign of Perfection. ‡ For it is a most true and certain divination, neither doth it proceed from nature or human arts, but from purified minds, by divine inspiration. We shall now discuss and examine Prophesying and Oracles.
189:* "Ninth Number."—The Ninth House of the Horoscope, known as the House of Science and Religion.
189:† "Revolution."—When the Sun has attained, as to the Earth, its original position, or the place it occupied at the moment of birth.
189:‡ "Sign of Perfection."—This is the First House of the Horoscope: that House of the "Heaven," or Zodiac, "rising" at birth; the eastern horizon.