It is neither wealth nor splendor, but tranquility and occupation, which give happiness.

Thomas Jefferson (1743-1826) American political philosopher, polymath, statesman, US President (1801-09)

Letter to Anna Jefferson Marks (12 Jul 1788)
    (Source)

The salutation is "My dear Sister," and is a congratulations for her marrying Hastings Marks. Some copies, and filings of the letter, make it out to "Anna Scott Marks," her birth name was Anna Scott Jefferson.