In 1815, Cardinal Angelo Mai made an extraordinary discovery in the Ambrosian Library in Milan. He spotted that a book containing the records of the First Church Council of Chalcedon in ad 451 had been made out of reused parchment. The earlier writing on each sheet had been erased (washing with milk and oat-bran was the common method), and the minutes of the Church Council copied on top. As often in reused documents of this kind, the original text had begun to show through the later writing, and was in part legible.
It turned out that the recycled sheets had come from a very mixed bag of books. There was a single page of Juvenal’s Satires, part of Pliny’s speech in praise of Trajan (the Panegyric) and some commentary on the Gospel of St John. But the prize finds, making up the largest part of the book, were faintly legible copies of the correspondence of Marcus Cornelius Fronto, one of the leading scholars and orators of the second century ad, and tutor to the future emperor Marcus Aurelius, who reigned from 161 to 180. The majority of the letters in the palimpsest were between Fronto and Marcus Aurelius himself, both before and after he had ascended to the throne. Unlike the passages from Juvenal and Pliny, these were entirely new discoveries.
Fascinating. From a review by Mary Beard of a new book on Marcus Aurelius.