Maurice, Prince of Orange
Van Ceulen moved to Delft most likely in 1576 to teach fencing and mathematics and in 1594 opened a fencing school in Leiden. In 1600 he was appointed the first professor of mathematics at the Engineering School, Duytsche Mathematique, established by Maurice, Prince of Orange, at the relatively new Leiden University. He shared this professorial level at the school with the surveyor and cartographer, , which shows that the intention was to promote practical, rather than theoretical instruction.