The Royal Society, founded in London in 1660 and one of the world's oldest scientific institutions, is marking the start of its 350th year by putting 60 of its most memorable research papers online. Several of these documents include papers by Sir Isaac Newton, Benjamin Franklin, and even Antonie van Leeuwenhoek.
Click "source" above to download Leeuwenhoek's "Observations, communicated to the Publisher by Mr. Antony van Leewoenhoeck, in a Dutch Letter of the 9th of Octob. 1676, here English’d: Concerning little Animals by him observed in Rain-Well-Sea- and Snow water; and also in water wherein Pepper had lain infused."
Click here to view an audio slide show produced by the BBC that highlights some of the Royal Society's most precious items.
(Thumbnail of Leeuwenhoek via http://www.ucmp.berkeley.edu/history/leeuwenhoek.html.)