In his final letter to his wife before he vanished on Mount Everest a century ago, George Mallory tried to ease her worries even as he said his chances of reaching the world’s highest peak were “50 to 1 against us.”

The letter, digitized for the first time and published online Monday by his Cambridge University alma mater, expressed a mix of optimism while describing his exhaustion and the difficulties his expedition encountered on their quest to be the first party to conquer the peak.