A cloud chamber is a device particle physicists use to study subatomic particles that cannot be observed directly. But as they pass through the chamber, the particles bump into the cloud droplets, leaving an observable trail.
The Zendo serves as our cloud chamber, and the trail we watch out for is a trail of anger, pain and disappointment. These traces let us know that an expectation — even an unconscious expectation about how we should be, be treated, be able to handle ourselves, etc. — has passed through. Because even if we can't initially put our finger on an exact way to put the expectation into words, we know when we're in pain or angry.
Gradually, the more we study the traces in the Zendo cloud chamber, the more we will be able to discern patterns of expectation, patterns we call our core beliefs.
And then, as we notice them more and more directly, we can notice and label them simply as arising and passing thoughts, thoughts that do not need to be changed or eliminated, but simply watched as part of our mental landscape.
And at last we are present in that landscape, not because we have designed or learned to control it, but because we ourselves are the landscape and are at home in ourselves.