An alchemist is a person versed in the art of alchemy. By the middle of the 7th century alchemy was almost an entirely mystical discipline. He spent much time on alchemy, divination and Hermetic philosophy. Some touch upon alchemy, astrology, and related concepts. The elemental system used in medieval alchemy also originated with Jabir. Other objects relate to alchemy, geometry or numerology. This doctrine influenced medieval medicine, pharmacy, alchemy and also heraldry. The use of quintessence became popular within medieval alchemy. Homberg practised natural philosophy at a time of transition between alchemy and chemistry. Beliefs related to the alicorn influenced alchemy through spagyric medicine. It is still used today in alchemy and chemistry labs. It was the start of differentiation between alchemy and chemistry. Jung linked active imagination with the processes of alchemy. This was at a time when there was no clear distinction between alchemy and science. His book, "Rasendramangalam", is an example of Indian alchemy and medicine.