Before the introduction of electricity in the 20th century, candles were the most important light source. Traditionally, candles were made from foul-smelling animal fat or tallow often saved from cooking. In Egypt, torches and candles were made by soaking or dipping a papyrus core in fat. Primitive candles were used by everyone from common people to royalty and temple priests. Egyptians had extensive knowledge of perfumery, essential oils, and natural resins. Plant resins were an important trade commodity and essential oils were used extensively for personal hygiene. The first scented candles combined the art of perfumery with wick technology used for oil lamps. Because tallow candles were foul-smelling, the addition of scented oils was a practical necessity of the time.