If one were to be very precise, my 'theory' might be just a 'hypothesis', but in practice it doesn't really make a great difference.
I am critical about this theory/hypothesis, and I am still collecting evidence. There are several important sources that I have not yet been able to access, which may either help nothing at all, or provide relevant further evidence.
With respect to the question:
Quote:isn't the fact that Rudolf II ever owned the manuscript about as well established as the reported opinion by the same Mnišovský in the same (Marci to Kircher) letter that the author was Roger Bacon? I mean, could they both be just guesses?
the answer is a definite 'no'.
The Marci letter clearly expresses the first as a statement of fact, and the second as a statement of opinion.
With respect to Kelly, there is quite some literature about Widemann, where this is reported.
I have a scan of a short notebook of Widemann with alchemical recipes, where there should be a reference to Kelly, but I have to admit that I could not identify it.
Kelly remains a difficult person, especially if one tries to find out what he really was about. However, it is well established that for a long time he was one of the most respected alchemists for Rudolf and for the Rosenbergs. Even if he most probably fooled them.
Finally, with respect to David's question about catalogues and known purchases, this is where it gets really interesting, and it is also not possible to adequately describe it. I will have to keep that for the hypothetical occasion that I do find some positive confirmation.
Rudolf basically had two book collections, there was one more (the imperial library in Vienna) to which he contributed and could claim access, and another which belonged to the Habsburgs but he had no rights whatsoever (Ambras collection).
Of the first two, there are several catalogues of one (the Kunstkammer) and none of the more interesting second one
There is a *huge* amount of archival information about his purchases of just about anything, including books. In 2012 I knew of about 20 book references (this is also the state of the information at my web site) but I have a lot more now. It is possible to link numerous of these purchases to the Kunstkammer or to the Viennese library, but of course not to the uncatalogued collection(s).
There are numerous publications about all this. A good recent article is:
Richterová, A.:
Alchemical Manuscripts in the collections of Rudolf II. In: You are not allowed to view links.
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The state of my research can be summarised as follows:
- Among the known records of book acquisitions by Rudolf, this very much seems to be the most likely one
- The ratio between known records and undocumented book acquisitions remains unclear, but has improved a lot since 2012
- There is only a lukewarm indication that this particular sale could be it, and I need something much more concrete before I would make more definite claims.