The ancient Egyptians believed that after death, a person's spirit or 'ka' would travel during the day and return to its body at night. To ensure the ka could recognize its body for eternity, Egyptians developed the practice of mummification. The complex mummification process took 70 days and involved removing internal organs, dehydrating the body with natron, and wrapping the body in linen bandages with amulets. The preserved body was then placed in nested coffins and buried with supplies for the afterlife.