Before “Where’s Waldo?” there was the “moon maiden,” a shadowy figure hiding in the Ransom Center’s current exhibition, Other Worlds: Rare Astronomical Works.

One of the exhibition’s highlights is a first edition map of the moon rendered by Giovanni Domenico Cassini from 1679, the rarest edition of the first published moon map. The “moon maiden,” “a tiny female silhouette,” is most likely the playful work of Cassini or his engraver. To produce this detailed map, Cassini relied on the latest telescopic observations of the moon’s craters and mountains, among other features.