After you beat the game Atruis will tell you you can go back to Myst to play around. Go to the cauldron and enter 40 hit the front button on the cauldron then hit the back button. Go to the nuber enterer and press the hinge on the bridge to the spaceship go to the spot and enter 2735 and head up to the library to get to the Rime age. Use your Myst solving skills to get to the elevator. Go to the top floor and look inside for the button to Catherines room. Inside you'll find a gem puzzle. Solve it and find the video.