I'm currently studying in Vienna and have discovered that the Hapsburgs were "buried 3 times." Most of the dynasty's bodies are in the Imperial crypt, yet their hearts are in the Church of the Augustinian Friars and their other organs are in the catacombs underneath the Stephansdom.
I can't seem to find anything online related to why the Hapsburgs did this, so I was wondering if there are any theories. Furthermore, I'm wondering if this practice is related to the ancient Egyptians, similar to the adoption of historicistic Greco-roman architecture.
I don't believe there was any exceptional effort to preserve the bodies, aside from sealing the organs in jars filled with an alcohol mixture. What I remember from touring the Stephansdom catacombs is that the entrails are interred there as a sign of the church's status, similar to the relics of saints kept at the various altars in the main cathedral.