Before the days of the strip-mall Kung Fu Dojo, some martial artists earned a living by performing in travelling circus shows. These artists demonstrated seemingly miraculous feats to entertain their audience, and attributed them to esoteric qigong training.
Truthfully, these “vagabond skills” are mostly cheap parlor tricks. In this video clip, Wing Chun instructor Leung Ting demonstrates the (relatively) safe and easy way to break bricks with your bare hands, and slice yourself with sharp blades.