At the end of one of Robert Bunsen's courses, an unfamiliar student presented his certificate for the professor's endorsement. "But, Herr Dingskirch," Bunsen said, reading his name, "I have not seen you at any of my lectures."
"No," the young man remarked. "You see, I always sit behind the pillar." "Indeed," Bunsen replied, signing his papers with resignation. "A lot of you sit there."