"Primary sources are materials produced by people or groups directly involved in the event or topic under consideration, either as participants or witnesses. These sources provide the evidence on which historians rely in order to describe and interpret the past...By examining primary sources, historians gain insights into the thoughts, behaviors, and experiences of the people of the past.
Note: If you are using a collection of documents brought together in a single volume, the preface, introduction, and other materials written by the editor are considered secondary sources; however the documents themselves....are primary sources."
Taken from Mary Lynn Rampolla, A Pocket Guide to Writing in History, 8th ed (Boston: Bedford/St. Martin's, 2015), 9-10.
Here's just a small sampling of books with primary source documents: