In his lifetime, Sir Francis Drake had a diary which contained a lot of information pertaining to his various adventures as an explorer. Nathan Drake, a self-proclaimed descendant of Francis Drake, found the diary inside the explorer's empty coffin at sea, proving his theory that his supposed ancestor had faked his death.
The diary aided Nathan Drake greatly in tracking down the treasure of El Dorado. Francis Drake had previously set out to find the statue himself, and his diary contained detailed logs and clues that Nathan used to decipher the puzzles found on Versteckte Insel. The diary was damaged when Victor Sullivan was shot by Gabriel Roman, as it was being kept in the former's breast pocket and blocked the bullet from penetrating through his chest, inadvertently saving his life.