It was the custom of the chassidim of the second Rebbe of Chabad, Rabbi Dovber of Lubavitch, to pray quietly and gently, singing Chassidic songs as they prayed.
One of these chassidim, though he did not have any deep understanding of Chassidic thought, was also accustomed to pray with great feeling. While he would pray, he would sway tremendously. Being that he would hold on to the table that he prayed at, the table would shake as well.
Rabbi Dovber once remarked about this chossid: “His swaying during his prayers are sustenance for the heavenly angels.”
(Sefer HaSichos, 5703 pg. 125)