The original account of the moment that Sir Isaac Newton got clunked on the head by a falling apple has gone online for the first time.
The manuscript of William Stukeley's biography of Newton describes how Newton explained the theory of gravitation to him as they sat in the sunshine in Newton's garden.
Royal Society president Lord Rees said: "Stukeley's biography is a precious artefact for historians of science."
"He told me, he was just in the same situation, as when formerly, the notion of gravitation came into his mind. It was occasion’d by the fall of an apple, as he sat in contemplative mood," reads the fragile eighteenth-century manuscript.
"Why should that apple always descend perpendicularly to the ground, thought he to himself. Why should it not go sideways, or upwards? But constantly to the earth's centre? Assuredly, the reason is, that the earth draws it. There must be a drawing power in matter."
Of course, not all Newton's scientific ideas were quite so spot-on. He spent most of his time looking for ways to turn lead into gold - although, as this wasn't exactly popular with the authorities, he didn't shout about it too much.
Other documents newly published on the Turning the Pages website include the Constitutions of Carolina and Henry James's sketches of fossils.