For Newton, the author secured the first edition of his seven-volume correspondence, published by Cambridge University Press between 1959 and 1977 and now available in paperback on demand. Einstein's letters are still being published: "The Collected Papers of Albert Einstein," an ongoing series from Princeton University Press, has reached its 17th volume, covering June 1929 to November 1930. Earlier volumes in the series turned up previously unknown letters to Einstein's partner Mileva Maric, including references to a daughter whose existence had long been hidden.

Darwin's correspondence, also published by Cambridge University Press, reached its conclusion in 2023 with a 30th and final volume, completing a collection of more than 15,000 letters spanning his life up to his death on April 19, 1882.

Darwin's last letter, written on April 10, 1882, went to American geologist J. E. Todd, asking for seeds for his research on Solanum rostratum flowers. He died nine days later. His wife, Emma Darwin, wrote to Joseph Dalton Hooker, director of the Royal Botanic Gardens at Kew, on April 20, 1882, describing her husband's final hours and her own grief.

The final volume also recovers a letter from Charles Lyell, referred to as the father of modern geology, dated September 1, 1874, in which he sets out suppressed views on prayer and the afterlife.

Darwin's last book, "Earthworms," was published the same year he died. A Spanish edition, "La formación del manto vegetal por la acción de las lombrices," was published by KRK in 2009.