Spiritual healing: Fascinating colorized images show Navajo men wearing eerie masks of the gods used during a medical ritual in the early 20th century

Edward S Curtis was paid $75,000 in the early 1900s by J P Morgan to document the North American Indians. He spent the next 20 years observing their culture, taking more than 40,000 images of 80 different tribes. This series examines the Navajo Night Chant, a healing ceremony involving masked men dressed as deities. The ritual lasts for nine days during which the patient is regularly sweated and attended by the masked figures.