From Jeremy Bernstein's review of noted physicist Victor Weisskopf's 1991 memoir. Bernstein first took a class from the utterly brilliant and impenetrable Nobel laureate Julian Schwinger at Harvard. After a couple of days of withstanding the barrage, Bernstein decided to attend Victor Weisskopf's class at MIT. The result is endearingly described:
My visits to Viki's class in quantum mechanics at MIT were, in every way, a culture shock. The class and the classroom were both huge—at least a hundred students. Weisskopf was also huge, at least he was tall compared to the diminutive Schwinger. I do not think he wore a jacket, or if he did, it must have been rumpled. Schwinger was what we used to call a spiffy dresser.The trick in any class is not to let the students know how much you know (the Schwinger technique) but to let them know how much you, and indeed everyone else, do not know.
Weisskopf's first remark on entering the classroom, was "Boys [there were no women in the class], I just had a wonderful night!" There were raucous catcalls of "Yeah Viki!" along with assorted outbursts of applause. When things had quieted down Weisskopf said, "No, no it's not what you think. Last night, for the first time, I really understood the Born approximation." This was a reference to an important approximation method in quantum mechanics that had been invented in the late 1920s by the German physicist Max Born, with whom Weisskopf studied in Göttingen. Weisskopf then proceeded to derive the principal formulas of the Born approximation, using notes that looked as if they had been written on the back of an envelope. Along the way, he got nearly every factor of two and pi wrong. At each of these mistakes there would be a general outcry from the class; at the end of the process, a correct formula emerged, along with the sense, perhaps illusory, that we were participating in a scientific discovery rather than an intellectual entertainment. Weisskopf also had wonderful insights into what each term in the formula meant for understanding physics. We were, in short, in the hands of a master teacher