I assumed this was about the European (maybe only English?) practice of keeping mummified cats in a gap in your house to keep away witches. Dunno what topic is more grim, millions of potentially catless years or a mummified cat in your walls.
Do you have a source on the fact that this was done intentionally?
I only knew that cats go into hiding then they feel their end is near, that they do this on their own. Thus most "cat is missing" posters actually mean their cat died but kept it secret from its humans.
I found a mummified cat when renovating a house in Northern France. Always thought the cat must have eaten rat poison/poisoned rat and therefor mummified. How are these preserved? It didn't look embalmed in anyway.
I tried to look up an answer, the first page suggests they just stuck them in there. Then I decided I've seen my fill of dried cats for today so someone else can look it up.
