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 Text Collections when you have narrowed your topic and can provide specifics such as:
But you can also search using good keywords. For example:
Result: "Emigration to Canada." The Age (London, England), Sunday, September 28, 1834; pg. 311. New Readerships.
NOTE: terms, titles, and names might vary between time periods and translations. You might have to look for variants.