The idea of such an order, exemplified by the network of astronomers, professors, mathematicians, and natural philosophers in 16th-century Europe promoted by such men as Johannes Kepler, Georg Joachim Rheticus, John Dee and Tycho Brahe, gave rise to the Invisible College. This was the precursor to the Royal Society founded in 1660.[19] It was constituted by a group of scientists who began to hold regular meetings to share and develop knowledge acquired by experimental investigation. Among these were Robert Boyle, who wrote: "the cornerstones of the Invisible (or as they term themselves the Philosophical) College, do now and then honour me with their company...";[20]