The history of science contains many tensions, but none is more engaging than those between established mastery and inspired youth, between persons with formal education and those who've taught themselves. Jonathan Horrocks was an inspired young autodidact whose keen observations of Venus's transit across the disk of the Sun corrected errors in Kepler's calculations. In consequence Horrocks accurately predicted, contra Kepler, the transit of 1639 and (wtih his friend, William Crabtree) became the first astronomer ever to observe a transit of Venus. This new translation of Horrocks's Venus in sole visa, and the associated commentary, will not only illuminate a crucial period in the history of astronomy, it will also shed light on the spirit of scientific inquiry, embodied in a young scientist of ingenuity and mathematical rigor.