"he had embalmed her"

Egyptian Mummy, British Museum
GNU Free Documentation LicenseEgyptian Mummy, British Museum - Credit: Klafubra
 Embalming is a technique used to preserve human remains and delay the onset of decomposition.  It is usually performed so that the deceased can be placed in an open casket at the funeral and viewed by loved ones.  It has been a cultural practice for a long time - as seen in the Egyptian process of mummification.  Other cultures and religions have had their own customs and rituals surrounding the practice; some forbid it.  To train in embalming is complex and requires knowledge of anatomy and chemistry, along with a certain creative aptitude.  It takes several hours to complete a successful embalming.  It would seem the Marquis did so an extension of his pleasure - a sick labour of love.