Context: I was casually looking through some old questions when I found this question. The OP wanted a compound that has all the hydrates ranging from monohydrate to decahydrate. I found chromium(III) sulfate [$\ce{Cr2(SO4)3.$x$(H2O)}$ where $x=0,\ldots,18$] to be suitable. But, the actual formula of the compound is $\ce{[Cr(H2O)6]2(SO4)3·6H2O}$, so 6 of the 18 molecules are present as water of crystallization. So, I wondered, what is the maximum number of water molecules that can present in a compound as water of crystallization?
I can agree to what @BuckThorn said in his answer. It might be protein crystals. Wikipedia also supports the fact:
Compared to inorganic salts, proteins crystallize with large amounts of water in the crystal lattice. A water content of 50% is not uncommon for proteins.
Now, the question is what protein has the maximum number of water molecules as water of crystallization?
I did some cursory searches and looked for inorganic hydrates (see edit history: 36-hydrate is maximum I could find). I am also looking for such compounds which is in inorganic domain.