Mathematician, engineer, astronomer and geographer born in Trapani, Ximenes studied at the local college of Jesuits and joined the Society of Jesus who sent him to the Tuscan province. Eclectic mind, Ximenes was a hydraulic engineer (he was responsible for the start of the reclamation of the Maremma in Tuscany and the Paddle di Bientina) and civil engineer (roads in Tuscany are still made according to his plans). In 1765, during the reclamation of the Maremma, he planned the construction of the “Casa Rosa”: a structure used to manage the flow of water between the marshes and the Tyrrhenian Sea.
As astronomer, Ximenes took charge of the study of the obliquity of ‘elliptic’ and restored the gnomon of Santa Maria del Fiore in Florence. While teaching at the University of Florence, he began courses in hydraulic engineering and invented tools to measure the speed of the water. Among his inventions, the fan and the hydraulic valve, which allowed him to measure the precise speed of the current.
Ximenes was also a writer and a member of several international academies (Verona, Siena, Paris, Petersburg). From 1750 to 1759 he worked with the Jesuit Venetian Francesco Antonio Zaccaria for the publication of the literary magazine “Storia Encyclopedia d’Italia”. In particular, Ximenes worked on the drafting of the pages dedicated to science.
In 1756 he founded in Florence the observatory of “Saint John”(or Ximenian Observatory) to which he dedicated the last years of his life and now, therefore, bears his name. It is still one of the most important in Europe and there is preserved the library of Ximenes.
Ximenes was recognized by the scientific and intellectual greats of his time, so much so that the Grand Duke of Tuscany chose him as a geographer and engineer. Leonardo Ximenes died on May 3, 1786 of a stroke. In his will, he destined library, tools and income of its properties in Sicily to the institutes of astronomy and hydraulics, under the supervision of the fathers Stanislaw Canovai and Gaetano del Ricco. The two institutes will remain active until the middle of the nineteenth century. In gratitude, the Florentines erected a marble bust, placed in the observatory of St. John.