Sweet smelling plant materials have attracted human attention since ancient times. It was realised that some plant materials have a better aroma when placed on burning firewood, which is how rituals all over the world came to include both plants and incense. The ceremonial feeding of the perpetual fire in Zoroastrian fire temples, performed five times in 24 hours, is called būy (aroma). The ancient Iranian scriptures – the Avesta and scriptures written in Pahlavi – all mention aromatics and several kinds of incense.