But not its contents, that not being the object of the Samyama.
In plain words: Focusing on someone's body shows what kind of mind they have, but not the actual thoughts inside it. To know those, the yogi must focus on the mind itself as well.
He would not know the contents of the mind by making a Samyama on the body. There would be required a twofold Samyama, first on the signs in the body, and then on the mind itself. The Yogi would then know everything that is in that mind.
Namaste.
A calm guide to life, the mind and the old teachings.