Mac Lethal describes himself as "an imaginative rapper trying to take rap to a new horizon."
In his attempt to do that, he tries to rap without breathing for 90 seconds.
The video below starts with him explaining how he's going to do it, and training for the challenge. He starts spitting breathlessly at about the 3 minute mark.
He doesn't quite make it.
Still, 77 seconds is pretty impressive.
If you recognize Mac's name, it's because he's scored some pretty big viral hits in the past.