This section is from the book "A Compend Of The Principles Of Homoeopathy", by William Boericke. Also available from Amazon: A Compend of the Principles of Homoeopathy as Taught by Hahnemann.
At first, Hahnemann prescribed the usual doses (Ipecac, five grains, Nux four grains, Cinchona Bark one to two drams), he soon found that aggravation would follow such dosage, if they were chosen according to the similar relationship to the diseased process. This led him naturally enough to a reduction of dosage, and as he obtained equally good or better results, he kept on decreasing the amount. Yet the transition from the crude dosage to comparative infinitesimal quantities was quite sudden, within one year from 1798 to 1799, he advocated both. For a quarter of a century, Hahnemann gave his remedies in varying potencies, seldom as high as the thirtieth potency, * more frequently between the first and twelfth potency, sometimes descending to more material quantities.
But after he had incorporated the psora theory into his doctrinal edifice, he fixed upon the thirtieth potency as the uniform standard for the dose of all remedies. This was to be given in globules saturated and subsequently dried. He desired uniformity among homoeo-pathists, "and when they describe a cure, we can repeat it, as they and we operate with the same tools. Thus our enemies will not be able to reproach us with having no fixed normal standard". And at the same time, he disapproved of attenuations beyond the thirtieth in these words: "There must be some end to the thing, it cannot go on to infinity".
Whatever the size of a dose of a homoeopathic remedy, there is one point which must characterize it, i. e., it must be sub-physiological, that is, just short of producing symptoms.
* See chapter on the preparation of medicines.
Hahnemann's recommendation of the thirtieth potency as the dose for all remedies and cases has not been followed by the school, and rightly so, because it is wholly arbitary and unphilosophical to adopt one potency for all drugs. The physician must here, as in the selection of the remedy, learn to individualize.