To unlock the safe in the monk's room for the first time you need to enter this combination: press Analog-Stick Left until you reach "2", then press X. Press Analog-stick Right until "7", then press X. Press Analog-stick Right until "1", then press X. Press Analog-stick Left until "2", then press X. If done correctly, each time you press X a blue light should turn on, until you see four blue lights and the elevator to the underground cemetery opens. The combination is the Monk's birthday as he states in the diary (27th day on the 12th month). You can now get the Book Of The Eons from the safe.