In the book Dark Spell, Jason Baldwin talks about his experience with a Hacky Sack.
Here is a quote from the book:
At Grimes, Jason picked up a Hacky Sack and found that, “right there where you lived, you had all the room you needed.” Gradually, kicking the Hacky Sack became a central, grounding, and comforting part of his life. “I don’t meditate,” he explained. “Not that I have anything against it. I just have no experience with that. So I’d just put my headphones on and kick the Hacky Sack for physical exercise, to—not tune out but—tune in. It’s like the same feeling you get when you go walking or jogging or biking. You get this oneness feeling, especially when you get caught up in it, and you’re not losing control of it, and an hour has gone by and you’re drenched in sweat, and you got to take a shower, and you feel good.”
And here is a video of Jason showing his Hacky Sack skills.