Palimpsest
Before cheap paper, when parchment was expensive and books were labor measured in months, scribes would scrape the ink off an old manuscript and write over it. The original text — sometimes centuries of accumulated thought — would be partially erased, partially visible, bleeding through the new work in fragments. These recycled manuscripts are called palimpsests, from the Greek palímpsēstos: “scraped again.” The famous ones are recovered now. Archimedes’ Method of Mechanical Theorems survived only because a 13th-century monk scraped most of it away and wrote a prayer book over it. The prayers were the intended text. The mathematics was the ghost. Centuries later, multispectral imaging revealed the ghost was more interesting than what had been written to replace it. ...