1. William Gilbert, De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure (published by Peter Short, London, 1600), Facsimile available from the Library of Congress via http://lccn.loc.gov/04001021 (permalink). English translation by Paul Fleury Mottelay (On the Magnet and Magnetic Bodies, and on That Great Magnet the Earth, 1893), Facsimile published by Dover Publications, New York, 1991, also available at http://www.gutenberg.org/ebooks/33810 (open access).
2. Otto von Guericke, Experimenta Nova (ut vocantur) Magdeburgica de Vacuo Spatio (“New (so-called) Magdeburg experiments on empty space”) (published by Johann Jansson van Waesberge, Amsterdam, 1672), in particular Book 4, Chapter 15, pp. 147–150. Facsimile available from the Smithsonian Institution via https://archive.org/details/ottonisdeguerick00guer (Open Library).
3. A Letter from Mr. Stephen Gray to Dr. Mortimer, Secr. R.S. containing a farther Account of his Experiments concerning Electricity;Stephen,1732
4. Benjamin Franklin, Experiments and observations on electricity made at Philadelphia in America by Mr. Benjamin Franklin, and communicated in several letters to Mr. P. Collinson, of London, F.R.S. (Printed and sold by E. Cave, at St. John’s Gate, London, 1751), in particular pp. 9ff. and Fig. V (on p. 87). Facsimile available at https://archive.org/details/experimentsobser00fran (Open Library).
5. Benjamin Franklin and lightning rods