Two thirteenth-century astrolabes: what does an inscription prove?
Compare instruments in London and New York. A dated inscription, a museum record, and a surviving treatise answer different questions about their history.
First astrolabe: London
The British Museum's record for astrolabe 1855,0709.1, made by Abd al-Karim al-Misri, gives a date of 1235 to 1236 CE in its current catalogue text. The curatorial note sketches the instrument's Greek invention and its transmission through Hellenistic and Byzantine texts translated into Arabic, with the earliest Islamic astrolabes and treatises in the ninth century. British Museum ↗
Then New York
The Metropolitan Museum's record for the Rasulid astrolabe of Umar ibn Yusuf dates it to 690 AH, 1291 CE, in Yemen. The museum notes that the object is unusually well documented and connected to an autograph treatise on astrolabe construction in Cairo, a rare link between an instrument and a text about making it. Metropolitan Museum of Art ↗
Object evidence and transmission claims
The research record uses the London astrolabe as material evidence for Islamic astrolabe practice, but flags that the Greek-to-Arabic transmission summarized in a curatorial note is a historical relationship needing source-chain evidence beyond one summary. It also notes that legacy catalogue pages have shown differing date renderings, which it preserves rather than hides.
Which date is stronger evidence?
Which is the stronger piece of evidence, a dated inscription on an instrument or a treatise describing how it was made? What does each one leave out?