realMyst: Masterpiece Edition

When you're in Sirrus' room in Stoneship Age facing the bed, you'll want to hide behind the plant to the right of the bed.

First, you'll Need to be in free-move mode.
Walk into the plant while looking up at the ceiling and you'll sort of glitch your way through it. Once behind it the achievement should pop.

You can get back out by again, walking into the plant while looking up.