The oldest known terrestrial globe extant is that constructed by Martin Behaim of Nuremberg in the year in which Columbus made his first momentous voyage across the Atlantic.[29] It is a manuscript globe, that is, a ball covered with irregular strips of parchment on which the world map has been drawn by hand and elaborately colored. In the first decades of the sixteenth century, numerous globes were made either of copper on which the map was engraved, of wood, or of a composition on which an engraved or hand drawn map was pasted. Some of these globe maps, as for example that attributed to Martin Waldseemüller and supposed to have been drawn in the first decade of the sixteenth century, hence the oldest known of this character, were engraved and printed on gores or bi-angles, and were so fashioned mathematically that they would completely cover a ball when pasted over its surface,[30] but not until Mercator, in 1541, engraved and printed his famous globe gore map can such a method be said to have proved itself to be thoroughly practical. From this time on, with now and then a slight modification of the number of gores employed and of the method of fitting them on the ball near the poles, globes have been constructed in much the same manner as Mercator had constructed his first example. That he made many globes is very certain, yet it appears that all of these were long thought to have been destroyed, until about forty years ago, when a complete set of his gores was found, and at present no less than six others, either mounted or unmounted, can be located.[31] In 1551, Mercator prepared in the same manner a celestial globe map, all examples of which likewise had been thought to have disappeared until the discovery of the set referred to above, and of this globe a number of copies are now known to exist. Quite as successful as Mercator were the van Langrens, father and son, the first globe of the father dating as early as 1585.[32] Before the close of the sixteenth century, Jodocus Hondius became interested in the construction of globes, and, like the van Langrens, continued his work in the first decade of the following century, his workshop then falling into the hands of his sons, who for many years found the manufacture of globes to be a profitable business.[33]