Constantijn Huygens wrote to Oldenburg about Leeuwenhoek and his own single-lens microscope

Date: 
February 12, 1674

Huygens wrote about two different microscopes in this letter, a complicated one that Swammerdam and Sijen struggled to use and Huygens's own simple microscope. All three visited Leeuwenhoek around this time.

Document: 

Huygens wrote the letter in French. The translation below comes from Hall & Hall's The Correspondence of Henry Oldenburg, p. 459.

I shall have an extract of your letter sent to Mr. Leeuwenhoek, who will be very glad of the warm welcome you give his observations and will thence find himself stimulated to push his industry further. Mr. Swammerdam and the Botany Professor Van Sijen ... are very much struggling with the microscope and ferreting out the intimate nature of plants, animals, etc. ...

These gentlemen use a very laborious microscopical device, which turns in every dimension on balls properly worked in copper. Nothing more finished can be seen, but I make light of them, opening their eyes with a very simple little device which I always carry in my pocket which gives me all that one could wish for by way of movements, with a needle to view objects in the air, or a plate to lay them flat, and nothing is easier.

Sources