A graphic representation of a surveying instrument conceived by Niccolò Tartaglia with a dioptra installed on top. The image shows the two phases of the measurement procedure used to calculate the distance between the instrument below (observer) and point A. The design and construction technique of this instrument, as well as instructions on how to use it, were added by Tartaglia to the Third Book in the second 1550 edition. From Niccolò Tartaglia, Nova scientia, Venetia, 1558, Third Book, 32r.