Inhale perfluorobutane if you want a voice even deeper than sulphur hexafluoride offers

It's widely understood, in the collective consciousness of the meme-anschauung, that inhaling sulphur hexafluoride is how one briefly attains an extremely deep and manly voice. But there is a gas that offers even deeper and manlier formants: perfluorobutane. Cody's lab:

"I breath in samples of sulfur hexafluoride and perfluorobutane which has nearly twice the density.