The Royal Society received Leeuwenhoek's first letter

Date: 
May 17, 1673

The Dutch Republic was using the new Gregorian calendar, so it was 17 May in Delft when the letter was received in London on 7 May. Even if the letter was not read aloud at the meeting, the members read it a few weeks later when Oldenburg published his translation in the next issue Philosophical Transactions, number 94, dated May 19, 1673. The next mention of Leeuwenhoek in Birch's History came on 22 November 1674 (12 November O.S.). The mention after that is 11 February (1 February O.S.) 1676, when the read the first part of Leeuwenhoek's Letter L-040 of 9 October 1676.

One of the attendees at that meeting was not a member of the Royal Society.

Signor BOCCONE, a Sicilian gentleman, who was well skilled in plants and petrifications.

Later on his tour of Europe, botanist Paolo Boccone (1633-1704) visited Leeuwenhoek (source: Con. Huygens).

Document: 

Birch's History, vol. III, p 88:

Mr. OLDENBURG produced a book of Dr. de GRAAF dedicated to the Society, intitled, Regneri de Graaf Partium Genitalium Defensio, together with a letter to Mr. OLDENBURG, dated at Delft in Holland, 28th April, 1673, communicating some microscopical observations of Mons. LEEWENHOECK.

 

Sources
Year Author Title
1673 Leeuwenhoek, A. van A Specimen of Some Observations Made by a Microscope, Contrived by M. Leewenhoeck in Holland, Lately Communicated by Dr. Regnerus de Graaf
1756 Birch, T. The History of the Royal Society of London