"William's chief reference... was A Complete System of Opticks, a two-volume work published in 1738 by Robert Smith, the same author whose [mathematics] book on harmonics [Harmonics, or The Philosophy of Musical Sounds] had captivated him more than a decade earlier. Smith explained the theory of optics but also gave step-by-step instructions on how to apply it to the construction and use of astronomical telescopes. ...word reached him that a Quaker gentleman who lived nearby was giving up his hobby, which just happened to be grinding telescope mirrors. William bought up his tools and some partially finished mirrors. The man gave him some lessons and then, armed with Smith's instructions, he went to work."