Mayan rituals were usually performed on astronomically significant dates. Human sacrifice was important to the Mayans. They believed that it was necessary for the sun, moon, and stars to continue moving. Mayans also sought advice through vision quests. Vision quests were done so that the vision serpents could contact the spirits and ancestors in the underworld. This was usually done with the aid of bloodletting, enemas, and hallucinogens. Bloodletting was very popular with kings and queens, as well as commoners. This was usually done with obsidian blades or stingray spines.