Sosan, also known as the Third Zen Patriarch, was a Chinese Zen teacher who lived in the 6th century. He is best known for his teachings on the concept of "original nature" and the practice of "silent illumination" meditation.

One of the key teachings of Sosan was the idea of "original nature," or the inherent Buddha nature that exists within all beings. He believed that this nature was pure and unchanging, and that through the practice of meditation, one could awaken to this true self and achieve enlightenment.

Sosan also emphasized the practice of "silent illumination" meditation, also known as "shikantaza" in Japanese. This practice involves sitting in a state of complete stillness and awareness, without any specific focus or object of meditation. It is a form of non-dualistic meditation, where the goal is to simply be present in the moment and observe one's thoughts and sensations without judgment or attachment.

In his famous poem "Hsin Hsin Ming," Sosan wrote, "The Great Way is not difficult for those who have no preferences. When love and hate are both absent, everything becomes clear and undisguised." This verse highlights the essence of Sosan's teachings, which emphasize the importance of letting go of attachments and preferences in order to see things as they truly are.

Sosan also taught the practice of "just sitting," which involves sitting in meditation without any particular goal or intention. This is similar to silent illumination, but with a more relaxed and open approach. The goal of "just sitting" is to simply be present and allow the mind to settle naturally without any effort or control.

In addition to these specific meditation practices, Sosan also emphasized the importance of mindfulness in daily life. He believed that the practice of meditation should not be confined to a specific time or place, but rather should be integrated into every moment of one's life.

In summary, Sosan's teachings on meditation revolve around the concept of "original nature" and the practice of silent illumination and just sitting. These practices emphasize the importance of being present and letting go of attachments and preferences in order to awaken to one's true self and achieve enlightenment.