1. Hooke Robert, The posthumous works, ed. by Waller R. (London, 1705), 557
2. Sprat Thomas, The history of the Royal Society (London, 1667), 246. It has also been attributed to Halley, see Ronan Colin A., Edmond Halley, genius in eclipse (London, 1970), 35-36.
3. Birch Thomas (ed.), The history of the Royal Society (London, 1756–57), ii, 113; Hooke, op. cit. (ref. 2), 503.
4. Reliable accounts of the various early configurations of reflecting instruments can be found in Cotter Charles H., A history of the navigator's sextant (Glasgow, 1983), 104–31, and in Ifland Peter, Taking the stars (Newport News, 1998), 12–18.