Citations:umbrae rectae et versae


 * 1995, Umberto Eco [aut.] and William Weaver [tr.], The Island of the Day Before (1998 Vintage Books republication, ISBN 9780749396664, chapter 24: “Dialogues of the Maximum Systems”, pages 307–308
 * This second was the most thrilling side. Thanks to it the observer could know that Horologium Catholicum mentioned before, with the hour at the Jesuit missions on every meridian; and further, it could also perform the functions of a good astrolabe, in that it revealed as well the quantity of the days and the nights, the height of the sun, the Umbrae Rectae et Versae, the altitude of the stars above the horizon, the quantity of crepuscules, the culmination of the fixed stars by year, month, and day. And it was through repeated experimentation here that Father Caspar had arrived at the certitude finally of being on the antipodal meridian.