Francesco di Giorgio Martini's sketchbook

[JustAnotherTheory]

Don't forget that di Giorgio Martini was Taccola's apprentice. He had first-hand access to all his manuscripts as his pupil. Maybe also the bridge scene from Palatino 766.

Plus as you can see in this thread, the architectural designs from Martini look like some of the elements of the VMS Rosettes.

So no, it's not "quite a massive leap" to think that the VMS was created at the very end of the 15th century, at least.