On this page of our guide to Psychonauts 2 you can view the locations of Nuggets of Wisdom appearing in Cruller's Correspondence.
There is only a single Nugget of Wisdom in this level.
Nugget of Wisdom 1
Location: Above the Typewriter.
To access this collectible, you need to jump on the lamp. Simply follow the path laid out by thoughts, cardboard boxes and envelopes.