The Mayas believed the four gods, the Bacabs, held up the sky. The Bacabs were also invoked to heal disease. Ritual of the Bacabs: A Book of Maya Incantations  is the first English translation of this Maya manuscript, dating back to colonial times.   Discovered in the early twentieth century, the manuscript's origins are traced to the golden period of Maya civilization. It contains incantations used to cure diseases of body and spirit, and it records the magic practiced among the Mayas--the most advanced Western civilization of antiquity.   As in other ancient cultures, the Mayas believed that sickness was the manifestation of an evil spirit, which required exorcism. The shaman recited powerful incantations to banish evil spirits and cure such afflictions as asthma, fevers, skin eruptions, and seizures. Ritual of the Bacabs provides an exciting and enlightening portrait of ancient Maya religion, medicine, and magic.