A parchment kept by Paolo of Genoa dated from at least the mid-13th century was hidden among other documents in a tin box secreted in a wall of St. Sophia in Constantinople. The most significant manuscript represented a stained glass window and Roman numerals. The reverse side of the parchment had writing in the Coptic alphabet, appearing to be some sort of cipher; as it turned out, these were related to the actual entrance of the Venetian catacombs underneath the Biblioteca di San Barnaba. On the top of the page, there was a crude drinking vessel with the Aramaic words 'father, son, holy ghost.' It also referred to the Holy Grail being guarded by a lethal protective device.
The 20th century scholar G. Codirolli later discovered the tin box. Knowing about Henry Jones, Sr's quest about the Holy Grail, he offered to show it to him. On his way to a lecture in the USA he traveled on board the Titanic. He survived its sinking in April 1912, and managed to salvage at least a part of the manuscript. He stopped by Las Mesas and delivered the document to Dr. Jones, allowing him to make a facsimile before he returned from his lecture on the west coast. Jones used it in his Grail lore studies, combined with the testimonies by Saint Anselm that spoke of "trials" that protected the Grail.
Behind the scenes[]
Transcription of the parchment, and possibly the cipher, in the Grail Diary. (Note: the window above is one out of six possible variations, and the instructions below are random)
The drawing referred in the description must be related to a puzzle in the Indiana Jones and the Last Crusade: The Graphic Adventure game, where Indiana Jones has to locate the correct stained glass window in the Biblioteca di San Barnaba. The image of the window does not appear in the game documentation, but only in the on-screen Grail Diary of the game. The exact drawing is random among six possible images.
The "Coptic cipher" is referred a couple of times in the game documentation by Henry. Hearing about the Coptic Gospel of Joseph of Arimathea he hopes to find some clue about it. However, the matter is left unanswered in the narrative of the Diary, nor does any Coptic cipher play a role in the game. It is possible, however, that the "cipher" is an obscure reference to the random combination that must be used to identify the right slab that leads to the Venetian catacombs.