The design for this tapestry kit is based on an eighth century fragment of silk serge, formerly in the treasure of the Sancta Sanctorum, where it was used as a cushion for the enamel cross of Pope Paschal (AD 817-824). The highly stylised nature of the design is typical of Byzantine art and textiles. The original is now housed in the Museo Sacro, Vatican, Rome, Italy.

According to Greek mythology, Pegasus sprang from the gorgon Medusa's neck when she was killed by Perseus. Pegasus then flew to mount Helicon, where, having struck the ground with his hoof, a spring began to flow which became sacred to the Muses. Bellerophon, King of Corinth, managed to capture Pegasus with a golden bridle, enabling him to destroy the three-headed monster Chimaera. Unfortunately, however, this caused Bellerophon to have an inflated opinion of his greatness, and he attempted to fly on Pegasus to join the gods on Olympus. An enraged Zeus sent an insect to annoy Pegasus, causing the horse to throw Bellerophon from his back. Pegasus was then installed in the Olympian stables where he was entrusted to bring Zeus his lightning and thunderbolts.