PG
Petrus Gyllius was a French scholar of the sixteenth century — topographer, translator, and explorer — remembered for his travels to the region of the Basilica Cistern. He was wont to set down the initials "PG" as his mark; and a French inscription carved into the cistern wall and signed "PG" was known by Jean-Zera for Gyllius's own hand. The company recovered what has been taken for Petrus Gyllius's diary, a volume that records a mechanism for the transference of water, makes reference to stairs beneath the cistern, avers that Justinian most likely disposed of the bodies of magic-users below it, speaks of a huge cage, names its author's travelling companions as members of a lodge, and closes upon a reference to a dreaded she-devil.