As I Heard Them, Vol. 1, p. 343, no. 42
My zeide described the time when a young man, bursting with joy, came out from yechidus with the Tzemach Tzedek and turned somersaults in the courtyard – for the Rebbe had said Chassidus in the meeting!
"How did that happen?" they asked him.
When he entered yechidus, the young man related, he said, "Rebbe, say Chassidus for me."
"What do you need Chassidus for?" the Rebbe asked.
"I need something to daven w ith."
"Meditate on how Hashem fills all worlds, how He encompasses all worlds, and how everything is utterly nothing before Him," replied the Rebbe.
Who was the young man? Bera, the Patzitzer Rav.