You can look in Text Collections for relevant primary sources.
The trick is to find a text collection that is relevant to your topic.
The Subject & Research Guides sometimes list relevant Text Collections.
If you happen to find a primary source publicly available on the web, verify its authenticity
It is best to search EEBO when you have narrowed your topic a little bit and can provide specifics such as:
But you can also see what happens if you type in good keywords:
In the Results List, the number of hits on the keyword are listed at the end of the record under the heading FOUND
Subscription text collections like EEBO are reliable.
NOTE: terms, titles, and names might vary between time periods and translations. You might have to look for variants.