This is a very good method of investigation; it produces a feeling during the process of realizing emptiness that is entirely new. Some people will break into tears at this time. Some people will find their own stupidity to be laughable: I have all along believed in the existence of a “self”; to sustain this “self,” I have committed a lot of wrongdoings and wasted my entire life; it is truly absurd! Thinking so, they cannot help but laugh. Although different, these reactions come from deep within; it is not because the scriptures say people will react this way that they do so intentionally. For whom would they need to put on an act? No one can tell if we are crying or laughing when we sit alone in meditation. When we enter a certain state of mind in the course of meditation, these reactions are spontaneous.

~Depicted from THE FOUR SEALS OF DHARMA - The Practice of Realizing Emptiness