https://en.wikipedia.org/wiki/Gunther_von_Hagens

He has a method of plastination that he has used for decades to preserve corpses, notably as the exhibition Body Worlds.

https://en.wikipedia.org/wiki/Body_Worlds

https://bodyworlds.com/

> and after this [the Persian spies] saw last of all their receptacles of dead bodies, which are said to be made of crystal in the following manner:—when they have dried the corpse, whether it be after the Egyptian fashion or in some other way, they cover it over completely with plaster 21 and then adorn it with painting, making the figure as far as possible like the living man. After this they put about it a block of crystal hollowed out; for this they dig up in great quantity and it is very easy to work: and the dead body being in the middle of the block is visible through it, but produces no unpleasant smell nor any other effect which is unseemly, and it has all its parts visible like the dead body itself.

https://en.m.wikipedia.org/wiki/Macrobians

Epoxy resin.

This is the kind of stuff that indie horror movies are made about.

Case in point: Body Worlds art exhibit by Dr. Gunther von Hagens, and the film Anatomy:

https://en.wikipedia.org/wiki/Anatomy_(film)

There's a bunch of "hush-hush" stuff about it, but it appears to just be very well-done standard mortuary stuff.

https://en.wikipedia.org/wiki/Lenin%27s_Mausoleum#Preserving...

(The patent is only 2 pages, and the 1pg text description doesn't address the question of anaerobic bacterial decay or the removal of water to solve decay that way, but it also only claims 'indefinite' preservation, so it's not necessarily claiming perpetual preservation. It could just be intended for a few months or years, and who knows how well it'd work?)

> All these methods of sealing the body into airtight contraptions ignores the fact that decomposition comes from within. When the heart stops, the autolysis, or self-digestion, of the flesh begins, through its enzymes consuming cell membranes. Trapping a body in with its own bacteria means it is producing gas that has nowhere to go.

One thing worth noting here is that this was the era of germ theory and vitamin-ization and initial success in blood/organ transplants (eg. https://www.amazon.com/Immortalists-Charles-Lindbergh-Alexis... ). There had been such huge gains in health that some of the projections and assumptions are hard to recognize (and are part of why science fiction from before the 1950s can be so strange to read). For example, given how pervasive germs turned out to be, and how deadly, but also how beneficial things like vaccination or pasteurization were, there was something of a vogue for imagining a future germ-free world: https://gwern.net/doc/genetics/microbiome/germ-free/2012-kir... This would help lead to greatly reduced sickness and mortality, and help extend lifespans to centuries. (After all, the contemporary fad of 'microbiome'-everything aside, mammals like mice or humans get along pretty well without any microbes, as we now know from the later germ-free animal research and bubble boys.)

You might ask how they imagined this working in practice, as sterilizing the entire world seems infeasible? Well, one idea was... Perfectly-sealed glass cubes, using similar techniques as germ-free animal or bubble boy environments. For example, the 1927 "The Machine Man of Ardathia" https://freeread.com.au/@RGLibrary/FrancisFlagg/Ardathia/The... imagines a far future germ-free man traveling back in time in his glass cube to inspect us short-lived disease-plagued primitives who wander around naked. So it's not a big step to imagine sealing them into a block for indefinite preservation post-mortem.