To reach the Mechanical Age, go to the southern edge of Myst. There should be a building in the water with a large clock on it and two wheels you can reach. The two wheels represent the hands on the clock, the large one controls the large hand and the small one controls the small hand. Click the small one twice and the large one eight times so that the clock says 2:40. Gears will come up from the water and allow you to access the building. Once inside, there will be three levers and a machine that says 3,3,3. The lever on the left turns the top two gears and the one on the right controls the bottom two gears.

Pull the levers until the machine says 2,2,1. If you pull the lever and nothing happens, pull the one on the far right to reset the machine. Once it says 2,2,1, the large gear on the northeastern part of the island should open up. Look inside it to find a linking book that will teleport you to the Mechanical Age.