The Chemical Shadow in the Book of Roger Bacon

It was bought from D, we know, by Emperor Rudolph II of Germany for 600 gold dukats. That's roughly $30,000 in today's economy. There are accounts that mentioned John D having come into a sum of money just a little bit bigger than this. An acid wash had been used on the pages to bring out the vibrancy of the ink,. But that that may have then washed away other writing in the book. It has changed hands quite a number of times.