The Natural History-Pliny the Elder-77CE

I have included in thirty-six books 20,000 topics, all worthy of attention, (for, as Domitius Piso says, we ought to make not merely books, but valuable collections,) gained by the perusal of about 2000 volumes, of which a few only are in the hands of the studious, on account of the obscurity of the subjects, procured by the careful perusal of 100 select authors; and to these I have made considerable additions of things, which were either not known to my predecessors, or which have been lately discovered.