Hans Sloane wrote Letter L-394 to Leeuwenhoek personally thanking him for the bequest of 26 magnifying glasses
Text of the letter in Alle de Brieven / The Collected Letters at the DBNL - De Digitale Bibliotheek voor de Nederlandse Letteren.
The date is New Style, which was eleven days ahead of the Old Style date of 16 September 1701 used by Sloane in London.
Sloane thanked Leeuwenhoek for some recently received letters. He added a personal word of thanks for the bequest of 26 microscopes to be received after Leeuwenhoek's death with reference to a separate letter of thanks of the president of the Royal Society, John Somers, which has been lost.
He added:
You by Yo.r glasses have first discovered to the society many extraordinary fine things many of which have afterwards been confirmed by other observers and farther that the society have very much depended upon what you say for truth which you have declared without being led away by the opinions of other men.
The manuscript is lost but a rough draft is in London's British Museum, Sloane MS, No. 4068, fol. 27-28. That draft is the one printed in Alle de Brieven / Collected Letters.