Voynich Decoded

[rikforto]

You could assume virtually any person of even petty money and power in Northern Italy or Europe broadly and arrive at the conclusion that they were interested in preserving their inheritance through fertility; familial succession was a widespread legal and cultural consideration. The only detail particular to Cosimo Medici is his surname, which was some 200 years established around the time of the manuscript and Cosimo's rise to power. Quite simply, one must wonder why he was not Cosimo Banchieri if we could deduce received family wisdom from European surname practices. Likewise, medical texts weren't usually composed by people with such startlingly on-the-nose names because, again, European surnames do not work like this. 

[paragraph ETA] And the idea that these practices "worked" is another level that demands extraordinary proof. Were there other copies? Is the text history wrong? Is there evidence that these practices were being used? Is there evidence of their efficacy? It is one thing to claim that it is medieval medical knowledge, it is several more substantial claims to attribute Medici dynastic success to its application and efficacy!

So, even granting your fertility interpretation of the manuscript, which itself remains very speculative while you defer providing the proofs you've alluded to, the interest in fertility and inheritance were not unique concerns of the Medici family. Likewise even granting that you could otherwise prove Medici authorship, their family name should be held as coincidental until further proof of transmission from the 13th Century is furnished. And without those charitable concessions, the entire theory looks like any number of other speculative analyses of the drawing; perhaps, if framed that way, interesting and worth carefully discussing, but about as far from proved as one can be while still holding a firm idea.