His Magnifying Glasses

Leeuwenhoek bequeathed twenty-six magnifying glasses to the Royal Society. They were duly described and catalogued, only to have "disappeared" from the archives by the mid-1800's. The rest, his will stated, should be sold "in a bundel".

Of the three hundred, at least (some sources say five hundred), magnifying glasses that Leeuwenhoek made, only nine are known today, plus an aalkijker whose provenance is not completely certain. The Boerhaave Museum in Leiden has the largest collection in any one place, and its library has the best collection of works about Leeuwenhoek.

In 2009, Christie's in London auctioned one of Leeuwenhoek's microscopes that had been on display in the Boerhaave, estimating pre-sale a high bid of 100,000 euro. It sold for 313,250 euro, the highest price ever paid for a scientific instrument from the Dutch Golden Age and a testimony to the significance of Leeuwenhoek today.

Van Leeuwenhoek's papers are lost. His will states:

It is our desire that in one box or suitcase will be closed up all the unpublished writings and letters, written by me, Leeuwenhoek, concerning my discoveries, and ten cut copper plates, belonging to some unpublished letters, for which was paid more than five hundred guilders as well as the translation into Latin, for which was paid seventy guilders and that so long as the villain [word deleted later by van Leeuwenhoek] Adriaan Beman is living, both those letters and those still to be written afterwards, may not be printed by his son or next of kin.

From 1693 to 1702, Leeuwenhoek had published half a dozen volumes of letters printed by his next door neighbor Henrik van Krooneveld. For his Send-Brieven in 1718, he used Adriaan Beman, and that relationship apparently did not go well.

After Leeuwenhoek's death, two other articles in Philosophical Transactions concerned him directly. Within a year, James Jurin published, in volume 32, "Some Account of Mr. Leeuwenhoek's Curious Microscopes, Lately Presented to the Royal Society. By Martin Folkes, Esq; Vice-President of the Royal Society".

Fifteen years later, Henry Baker wrote "An Account of Mr. Leeuwenhoek's Microscopes", which was published in volume 41, 1739. These two articles provide much of what we know about the microscopes, confirmed by direct analysis of the few surviving, which were probably not among those bequeathed to the Royal Society.