The ingredients of Indian yellow were a mystery until its secret was revealed in the 19th century. Prepared from the urine of cows fed only mango leaves and made exclusively in the Indian village of Mirzapur, the yellow pigment was refined by heating the liquid and pressing it into round balls.

https://www.theguardian.com/artanddesign/gallery/2017/jun/13/from-crushed-bugs-to-cow-urine-the-history-of-colours-in-pictures?CMP=fb_a-culture_b-gdnculture