This was not unlocking by simply finding a secret gem with the magic glasses on. What is needed to be done is:
-Go to 1-3 with your Magic Glasses equipped.
-The layout is usually random, but somewhere will be a twinkle that when hit a door will appear.
-Go in the door. This is a "bonus" room with a mini boss.
-Head to the top and kill the mini boss. It's fairly easy.
-Start shooting/attacking near the top far-left of the screen and a once invisible ledge will appear.
-The achievement should pop after this.