A "lost" science manuscript from the 1600s found in a cupboard in a house during a routine valuation is expected to fetch more than £1m at auction.
Dr Hooke's manuscript was hidden in a cupboard for 50 years
The hand-written document - penned by Dr Robert Hooke - contains the minutes of the Royal Society from 1661 to 1682, experts said.
It was found in a house in Hampshire, where it is thought to have lain hidden in a cupboard for about 50 years.
The owners had no idea of its value. It will be auctioned in London next month.
The Royal Society, Britain's leading academic institution, has said it had no hope of finding enough money to purchase the manuscript.
Dr Robert Hooke 1635 - 1703
Coined the biological word "cell"
Helped pave the way for the steam engine
Designed the sash window and the velocipede
Helped to rebuild London after the Great Fire of 1666
Accused Sir Isaac Newton of stealing his ideas about gravity
President Lord Rees of Ludlow has appealed for a "white knight" to buy the document, which contains more than 520 pages of script and some drawings, and make it available to scientists.
It was discovered in a private house where other items were being valued by an antiques expert and it was only as he left that the family - whose identity is being kept secret - thought to show him the manuscript.
"The valuer was just leaving when this document was produced from a cupboard," she said.
"All the vendor knows is that the document had been in the family as long as she can remember. She doesn't know how it got into the family."
Dr Robert Hooke, who died in 1703, has been described as the unsung hero of science and "England's Leonardo".
As one of the original Fellows of the Royal Society, Dr Hooke recorded hundreds of inventions, demonstrations and experiments by leading scientists, but his name is often forgotten.
Accused Sir Isaac Newton
The physicist, chemist, cosmologist, biologist, horologist and mechanic also published the world's first comprehensive illustrated book on microscopy and coined the word "cell".
He pioneered the modern watch, designed scientific instruments and devices, as well as the sash window, the velocipede, and the universal joint used in motorised vehicles.
He also helped pave the way for the steam engine and, with Sir Christopher Wren, was responsible for rebuilding London after the Great Fire of 1666.
However, he often fell out with other scientists accusing them of them of plagiarising his work.
His most famous feud was with Sir Isaac Newton, who he accused of stealing his ideas about gravity.
The auction is due to take place at Bonhams' sale rooms in New Bond Street, London, on 28 March.