Homeopathic Materia Medica are encyclopedia of therapeutic properties of each drug. These properties are ascertained through provings also known as Homeopathic pathogenetic trials (HPT). As per Samuel Hahnemann in his Organon of medicine § 143, homeopathic materia medica is " a collection of real, pure, reliable modes of action of simple medicinal substances, a volume of book of nature" They thus constitute a homeopathic prescribing reference guide and sources for compiling Homeopathic repertory. Earlier materia medicas have details regarding the materials and methods which may be used to prepare homeopathic medicines.