Richard Waller wrote to Leeuwenhoek about his recent observations and the structure of grass
Date:
February 2, 1692
Text of the letter in Alle de Brieven / The Collected Letters at the DBNL - De Digitale Bibliotheek voor de Nederlandse Letteren.
The original letter and drawing have been lost. Waller wrote it in Dutch. All of the other letters he wrote to Leeuwenhoek were in English.
The letter discussed letters received from Leeuwenhoek about the presence of air in the blood, the opening of the chyle-vessels into the intestine, and the occurrence of stones in the bladder. Waller described the structure of a grass-spikelet and enclosed a drawing he made (right; click to enlarge).