sources, one of mineral origin and one of animal origin. The latter was of special interest and he noted how cows were fed with mango leaves, suffered from the poor nutrition, with the sparse urine having to be collected in small pots, cooled, and then concentrated over a fire. The liquid was then filtered through cloth and the sediment collected in balls, then dried over a fire and in the sun. Importers in Europe would then wash and purify the balls, separating greenish and yellow phases. Mukharji also sent a sample to Hooker. Hooker had part of the sample examined by the chemist Carl Gräbe, who took considerable interest in its chemistry. In a 2018 publication, the analysis of part of this sample was documented. It confirms the animal origin of the sample and identifies the source as urine based on hippuric acid which is a key marker. The pigment can be clearly distinguished by spectroscopic techniques. The Art of Painting in Oil and Fresco, a translation of the French De la peinture à l’huile by Léonor Mérimée, states a possible source for the pigment:...the coloring matter is extracted from a tree or large shrub, called Memecylon tinctorium, the leaves of which are employed by the natives in their yellow dyes. From a smell like cow's urine, which exhales from this colour, it is probable that this material is employed in extracting the tint of the memecylon.In 1844, chemist John Stenhouse examined the origin of Indian yellow in an article published in the November 1844 edition of the Philosophical Magazine. At that time the balls of purree imported from India and China came in balls of around which when broken open showed a deep orange color. Viewed under a microscope, it showed small needle-shaped crystals, while its smell was said to resemble that of castor oil. Stenhouse reported that Indian yellow was commonly thought to either be composed of gallstones from different animals, including camels, elephants, and buffaloes, or deposited from the urine of some of these animals. He carried out a chemical analysis and concluded that he believed it was in fact of vegetable origin, and was "the juice of some tree or plant, which, after it has been expressed, has been saturated with magnesia and boiled down to its present consistence." In her 2002 book Colour: travels through the paintbox, Victoria Finlay examined whether Indian yellow was really