To attempt determine which homeopathic remedies would be best for various ailments, Hahnemann and others engaged in a series of provings.  In what can be viewed as early clinical trials of natural substances, Hahnemann and others self- administered pharmacologically active doses of many different substances, then carefully recorded the symptoms that resulted in a materia medica.  These provings were based on Hahnemann's early study of cinchona bark.   He states:

There is, therefore, no other possible way in which the peculiar effects of medicines on the health of individuals can be accurately ascertained ....  than to administer the several medicines experimentally, in moderate doses, to healthy persons, in order to ascertain what changes, symptoms and signs of their influence each individually produces on the health of the body and of the mind; that is to say, what disease elements they are able and tend to produce, since, as has been demonstrated , all the curative power of medicines lies in this power they possess of changing the state of man's health, and is revealed by observation of the latter.

Hahnemann felt that the best proving was done on oneself.  Since the proving is based on self observation Hahnemann cautions that the person doing the proving must be trustworthy, intelligent and have keen observational skills.  Some provings were taken from the literature, particularly where poisonings from a known agent produced a specific pattern of symptoms or lesions.  

Hahnemann stressed that homeopaths should add to the materia medica with his own provings:  

At first, about forty years ago, I was the only person who made the provings of the pure powders of medicines the most important of his occupations. Since then I have been assisted in this by some young men, who instituted experiments on themselves, and whose observations I have critically revised. Following these some genuine work of this kind was done by a few others. But what shall we not be able to effect in the way of curing in the whole extent of the infinitely large domain of disease, when numbers of accurate and trustworthy observers shall have rendered their services in enriching this, the only true materia medica, by careful experiments on themselves! The healing art will then come near the mathematical sciences in certainty.  (Organon, sixth edition)

However, most of the homeopathic provings that are currently referred to in the US Homeopathic Pharmacopoeia, which provide the basis for homeopathic prescribing, come from the time of Hahnemann.