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. On its top 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.