Context:

Referenced when discussing ancient knowledge of Qatar - 'Ptolemy, the great geographer, he produces a map that shows a place called Keturah, which is obviously Qatar as well.'

Context:

Referenced as a written historical source about Alexander. Arrian used Ptolemy's account, which the hosts discuss in relation to the story about talking snakes guiding Alexander to the oasis at Siwa.

Context:

Referenced as the work that Copernicus's De Revolutionibus was 'modeled very closely on' - mentioned when discussing how Copernicus presented himself as a Renaissance man looking to classical authorities.