10% of Medieval Manuscripts survive to this day - Is that an overestimate?

[Jorge_Stolfi]

It is estimated that scientific manuscripts like herbals, medicine, and other natural sciences, but also alchemy, had a moderate chance of surviving. They were valuable for learning and passed around among scholars and healers. Their survival rate is better than letters, manuals and stories.but less than religious matter. So while 10% is general estimate, class survival rates can differ quite a bit.

Sound plausible!  IIRC, part of John Dee's reports of conversations with "angels" (through a crystal ball, mediated by Edward Kelley) were used by the finder's cook to start the fire in the stove.

I once stumbled upon an essay on a medieval book by mathematician Nicole Oresme, of which at least 7 copies survived and are now in premier libraries: You are not allowed to view links. Register or Login to view.. Some of the copies have straight lines, even and clear handwriting, ornate capitals, etc; I suppose they were made for rich customers or for sale.  But the You are not allowed to view links. Register or Login to view. is interesting because it was apparently made or paid by a scholar or student for their personal use.  Like the VMS, the lines are tilted and crooked, the writing is uneven and sometimes unreadable, etc. -- yet the scribe marked out the first line of each paragraph by using a larger and distinctive "font" for the entire line.

Also, when sight-seeing in Prague I made a brief visit to the Strahov monastery.  Tourists could only You are not allowed to view links. Register or Login to view..  I was told that most of the bools there were still not cataloged.  A catalog of the library had been in the workd for years, but it got only a small fraction per year...

Also, I learned from the net that the Vatican Library had an absurd number of books, and the shelves were measured in kilometers.  IIRC, most was still not cataloged.

Also, I learned that the Sapienza university in Rome has a large collection of old books and manuscripts, but its not cataloged and there seems to be no catalog in the works.  That library was open to visiting scholars only a few hours a week.  I tried to contact the Prof in charge of it, but got no reply.  I fancy that Georg Bareš's grade reports may be in there somewhere...

And finally, I wonder sometimes that more books  may have been written before the printing press than after it.  Because someone who needed a book would often borrow it and copy it himself, or hire some scribe just for that copy; and then he would often skip parts that he did not need, change some parts he did not agree with, interpolate material from other sources, etc.  And many people chose to create their own book of observations or elucubrations -- rather than buy someone else's as we do today.  Whatever the VMS is, if its Author lived today, he probably would not have bothered to write that book...