The oldest surviving banknotes are examples of the "Da Ming tongxing baochao" (Great Ming Circulating Treasure Note), which were first printed during the reign of the Hongwu Emperor (1368–1398) – probably no earlier than 1375. These banknotes were not the first to circulate in China (similar promissory notes had been commonly issued since around AD 997), but they are thought to be the oldest to survive into the present day. The reason for the survival of these banknotes (they are actually quite common, with hundreds of examples existing in the collections of museums around the world) lies in the catastrophic hyperinflation of the early Ming Dynasty, which saw the value of each note plunge to around 1% of its original value by the 1420s. As this hyperinflation progressed, Chinese merchants went from needing only a few notes to needing bundles of them. When the currency collapsed in the mid-15th century, huge bales of now-useless banknotes were stuffed into jars, or wooden boxes, or left in old buildings and forgotten. It is possible that there are older Chinese banknotes in existence, but their current whereabouts are unknown. In 1915, for example, the American numismatist and antiquarian Andrew McFarland Davis (1833–1920) gave a presentation to the American Academy of Arts and Sciences that included photographs (reproduced in the official transcript) of Song Dynasty "Huizi" banknotes (c. 1165) from his personal collection. Davis died in 1920 and what happened to these notes is not known. Similarly, it was reported in 1987 that a Yuan Dynasty banknote from the 1330s had been found in the archives of the Hermitage Museum in St Petersburg, but this note (if it ever existed) appears to have vanished some time in the 1990s.