There was a renowned Zen master that once said that his greatest teaching was this: Buddha is your own mind. A monk was so impressed by how profound this idea was, he decided to leave the monastery and retreat to the wilderness to meditate on this insight. He found a cave and there he spent 20 years as a hermit probing the great teaching.
One day he met another monk who was traveling through the forest. Quickly the hermit monk learned that the traveler also had studied under the exact same Zen master. "Please, you must tell me what you know of the master's greatest teaching."
The traveler's eyes lit up, “Well, the master has been very clear about this. He says that his greatest teaching is this: Buddha is definitely not your own mind."