02
What it is
A sadhu board is a wooden board with hundreds of nails. You step onto it barefoot and stand for a few minutes. A guide is beside you, and so is a circle of people doing the same.
The practice comes from the austerities of India's sadhus. Today it is used as a tool: within a minute on the board you can see how you deal with pressure.
Is it safe?
The nails don't pierce the skin: your weight is spread across hundreds of points. The sensation is strong, especially in the first minute. You can step off at any second.