The main book collection will contain reprinted primary sources, which you can also use. Sometimes they are reprinted in "source books," which are collections of primary documents.
When looking for your topic, try adding "source*" as a title keyword or as a subject.
Examples:
The W&M Libraries subscribe to a number of Primary Source databases:
A number of universities have expertly curated collections of digitized primary sources too.
Please note: Any time you find documents online, be sure to evaluate the source is trustworthy.
Some examples include: