Lives and Opinions of Eminent Philosophers

Lives and Opinions of Eminent Philosophers by Diogenes Laertius (circa 300AD) is a biography of major Greek philosophers, including Book 10 on Epicurus. Contained within are:

• A letter from Epicurus to Herodotus entitled “A Summary of Physical Nature”
• A letter from Epicurus to Pythocles entitled “A Summary of Phenomena of the Sky”
• A letter from Epicurus to Menoeceus entitled “How to Live a Happy Life”
• The last will of Epicurus, outlining his final thoughts and disposition of his assets (and care of the children)

https://en.wikipedia.org/wiki/Lives_and_Opinions_of_Eminent_Philosophers