Once your legs no longer ache, you have really begun investigating Chan.

When you first learn how to sit in full lotus posture, if your legs feel stiff and painful, you may sit in a more comfortable manner. Thereafter, you should learn to sit in half lotus position. Then when your legs do not feel so painful, you can learn to sit in full lotus position. When your legs no longer ache, you have really begun investigating Chan. That marks the actual beginning. Basically, Chan investigation is intentionally looking for something to do when one has nothing to do. For instance, a cultivator who has eaten his fill, slept enough, is warmly clothed and has nothing else to do, will then investigate Chan. Getting good at it, we can then roam and play in the world.