In 1659, Robert Boyle commissioned the construction of an air pump, then described as a "pneumatic engine", which is known today as a "vacuum pump". The air pump was invented by Otto von Guericke in 1650, though its high cost deterred most contemporary scientists from constructing the apparatus. Boyle, the son of the Earl of Cork, had no such concerns—after its construction, he donated the initial 1659 model to the Royal Society and had a further two redesigned machines built for his personal use. Aside from Boyle's three pumps, there were probably no more than four others in existence during the 1660s: Christian Huygens had one in The Hague, Henry Power may have had one at Halifax, and there may have been pumps at Christ's College, Cambridge, and the Montmor Academy in Paris. Boyle's pump, which was largely designed to Boyle's specifications and constructed by Robert Hooke, was complicated, temperamental, and problematic to operate. Many demonstrations could only be performed with Hooke on hand, and Boyle frequently left critical public displays solely to Hooke—whose dramatic flair matched his technical skill.