Ancient Egyptians believed coffins could transform the deceased, not just contain them.
Notes on verification
Multiple independent academic and scholarly sources (ScienceDaily, American Research Center in Egypt, specialized Egypt tourism educational sites) all corroborate the transformative function of Egyptian coffins. The sources are consistent in describing coffins as magical vessels for transformation from human to deity/akh, not merely protective containers. Strong consensus across different types of sources.
Sources
- Ancient Egyptian coffins (wikipedia)