It isn't too hard once you understand what you are trying to do. When you first enter you will see a floating table that hovers above a point on the left side of the screen, your goal is to walk through a mirror and land on that floating table. I don't remember exactly how to do it, but you pull the levers to move the mirrors. Once you have set up the upper left mirror correctly (so it is directly above the point where the table floats) just wait until the table hovers below it, then walk through the correct mirror and it will drop you onto the platform. One thing that might not be obvious at first is that there are climbing walls on the right side of the room.