Wikitext

We get wikitext by action=parse and put it in the wikitext attribute.

• https://www.mediawiki.org/wiki/API:Data_formats
• https://www.mediawiki.org/wiki/API:Parsing_wikitext

The most direct way to get to wikitext is to add action=raw:
https://en.wikipedia.org/wiki/Abraham_Lincoln?action=raw&section=0

But this seems to fail if there is '.' in the title, e.g.
https://en.wikipedia.org/wiki/J._R._R._Tolkien?action=raw