Yang Xi
Although no autograph copies of Yang Xi's famous calligraphy have survived, one well-documented stone rubbing version of the revealed "Huangting jing" (黃庭經, Yellow Court Scripture) has been given special attention. The Song dynasty connoisseur and critic Mi Fu (1051-1107) analyzed four manuscripts of the "Huangting jing", and said the best one was written on a silk scroll with a provenance that he traced back to the early 8th century. Mi disagreed with a former owner Tao Gu (陶穀, 903-970) who said that Wang Xizhi wrote the manuscript, and concluded it was a superb example of calligraphy from the Six Dynasties period. The Ming dynasty calligrapher and painter Dong Qichang (1555-1636) was so impressed by the Mi Fu manuscript that he made a copy, recommend it as the best model for studying "kaishu" script, and included it as the first example in his classic "Xihong tang fatie" (戲鴻堂法帖, Calligraphy Compendium of the Hall of the Playful Goose). Dong's colophon attributed the calligraphy to Yang Xi himself and described it as "the traces of a holy immortal" (Ledderose 1984: 262-263, who calls Dong's attribution to Yang "extremely optimistic").
Archimedes
The foremost document containing the work of Archimedes is the Archimedes Palimpsest. In 1906, the Danish professor Johan Ludvig Heiberg visited Constantinople and examined a 174-page goatskin parchment of prayers written in the 13th century AD. He discovered that it was a palimpsest, a document with text that had been written over an erased older work. Palimpsests were created by scraping the ink from existing works and reusing them, which was a common practice in the Middle Ages as vellum was expensive. The older works in the palimpsest were identified by scholars as 10th century AD copies of previously unknown treatises by Archimedes. The parchment spent hundreds of years in a monastery library in Constantinople before being sold to a private collector in the 1920s. On October 29, 1998 it was sold at auction to an anonymous buyer for $2 million at Christie's in New York. The palimpsest holds seven treatises, including the only surviving copy of "On Floating Bodies" in the original Greek. It is the only known source of "The Method of Mechanical Theorems", referred to by Suidas and thought to have been lost forever. "Stomachion" was also discovered in the palimpsest, with a more complete analysis of the puzzle than had been found in previous texts. The palimpsest is now stored at the Walters Art Museum in Baltimore, Maryland, where it has been subjected to a range of modern tests including the use of ultraviolet and light to read the overwritten text.