Some people can see clearly that the mind is lucid and pure like a bright mirror.

Some need a year of practice and then the mind becomes lucid and pure. Others need three or five years and then the mind is lucid and pure.

Or some can attain enlightenment by being taught by someone else. Or some can attain enlightenment without ever being taught.

The Nirvana Sutra says: “The nature of the mind of beings is like a pearl which falls into the water. The water is muddy so the pearl becomes hidden. When the water is pure, the pearl is revealed.”