The drawings the pilot completes as a young boy are, on one level, symbolic of childhood imagination and the ways in which it is often discouraged: the adults who see the pictures mistake the first drawing for a hat and advise the pilot to return to a more "productive" activity after seeing the second image. Digging deeper, the two drawings also capture one of the central ideas in the book: "One sees clearly only with the heart. Anything essential is invisible to the eyes" (63). The first picture is an external view of a boa constrictor that has swallowed an elephant, while the second is a cross-section of the same subject. The second drawing, in other words, reveals the "essential" truth that is, strictly speaking, "invisible" in the first. The adults fail to see the point of even the second drawing, despite being literally able to see what it depicts. Meanwhile, the prince immediately grasps what the first drawing depicts without having to see the cross-section. These differences neatly encapsulate the idea that true understanding requires something beyond mere physical sight—for instance, imagination.