Retro reflection by transparent spheres, mentioned in Section 35.4 in the text, can be observed with dewdrops. To do so, look at the shadow of your head where it falls on dewy grass. Compare your observations to the reactions of two other people: The Renaissance artist Benvenuto Cellini described the phenomenon and his reaction in his Autobiography, at the end of Part One. The American philosopher Henry David Thoreau did the same in Walden, “Baker Farm,” paragraph two. Try to find a person you know who has seen the halo—what did they think?