Perhaps the most important book in science, Isaac Newton's Principia was published on this date (July 5) in 1687.
The folks over at Jodrell Bank have a nice video celebration of Isaac Newton and Principia in their latest Jodcast.
If you are looking for a good read on Sir Isaac Newton, you might try the book I am currently reading, Newton and the Counterfeiter: The Unknown Detective Career of the World's Greatest Scientist by Thomas Levenson.
To tie this all back to Palomar (after all that's what this blog is about) here is Palomar's 200-inch mirror with the crew of opticians who ground and polished the glass. In the center of the disc is a full-sized replica of the first reflecting telescope ever built, constructed by Sir Isaac Newton in 1671.