Complex sentence: The outside of the tombs were layered with white clay and charcoal; white clay layering was a practice that originated with Chu burials, while charcoal layering was a practice that was followed during the early western Han dynasty in the Changsha area.
Split into simpler sentences: The outside of the tombs were layered with white clay and charcoal. White clay layering originated with Chu burials, while charcoal layering was practiced during the early western Han dynasty in the Changsha area.