Where are the letters penned by Voynich?

[Emma May Smith]

The best argument is internal to the way Voynich dealt with the manuscript. He wanted it to be a lost work of Roger Bacon and stood to earn a great deal of money were it true. Voynich personally selected Newbold to study it, and he agreed with the attribution and spent years working to decipher it. If Voynich wanted his payoff he would have written a plain text that could pass as Bacon and enciphered it simply enough so Newbold would crack it quickly.

The alternative is that Voynich spent a lot of time and money making a fraud which was even then only half-baked. To believe the fraud theory you must hold that Voynich was at the same time a brilliant man and an idiot.