Yoga practices have ranged all over the place in 5000+ years. You've got chanting/kirtan, asana, pranayama (breathing/subtle energy exercises), drishti (gazing points), all manner of diet practices, and many many more. Putting the legs behind the head starts to look pretty tame. And, frankly, everything listed so far is positively boring when you consider the full spectrum of practices, especially those which have yet to, er, find an audience in the West.
So, how about this. Here are twenty practices. Some of them are real, some are not. We won't use their Sanskrit names. Hopefully by describing rather than naming them, we'll minimize any use of Google/Wikis. Who can identify the fakes? Bonus points for giving the Sanskrit names of the real practice (and, potentially, christening the fake ones with appropriate titles). A free class hangs in the balance...
1) Staring at a candle flame to force the eyes to water and thereby cleanse themselves.
2) Training the body to live directly on the energy from sunlight: no eating required.
3) Using leather strips to lash the legs into Padmasana for hours or days at a time.
4) Burial of a living yogi for days or weeks without food, water, or air.
5) Hands-free enema (container of water, squatting...you do the math).
6) Meditation (hours or days) while hanging from banyan tree branches (the higher the better).
7) Mouth/nose-guards worn 24/7 to prevent accidentally inhaling/harming small insects.
8) Living with/being accepted by animal packs.
9) Walking on water.
10) Holding one or both arms above the head until withered and atrophied.
11) Manipulating the tongue so its tip can touch the third eye (above and between the eyebrows).
12) Consciously stopping the heartbeat.
13) Psychadelic substances.
14) Meditation: seated in the ocean as tide comes in.
15) Digging ones own grave with the hands.
16) Counting the grains of rice in the village harvest.
17) Ritualized vomiting.
18) Creation and debate of hypothetical ethical dillemas.
19) Washing the intestines (outside the body).
20) Jumping back.
Yoga is some freaky sh*t.