Heisenberg was never sure whether or not he did it. Opticians do it visually. Opticians do it with their eyes. Particle physicists do it energetically. Particle physicists do it expensively.
Physicists do it a quantum at a time.
Physicists do it at two places in the universe at one time. Physicists do it attractively. Physicists do it energetically. Physicists do it in black holes. Physicists do it in waves.