In ancient India, even before the birth of Buddhism, there were already concepts of cause and effect, retribution, and reincarnation, and the practice of zazen (sitting meditation) existed.
There were also masters of deep mental concentration (meditative absorption or zenjō).
During Buddha's period of ascetic practice, he learned the "state of non-thought" (musōtei) from a master of zenjō. However, even after mastering the highest level of zenjō at that time, he was still unsatisfied, and undertook even more severe ascetic practices on his own.
Finally, he thoroughly awakened to the true nature of Nirvana. He was 35 years old at the time.
When Buddha attained enlightenment, he said, "Everyone possesses this eternal treasure. Truly, it is a wondrous thing!"
- Eternal treasure refers to the "mysterious mind of Nirvana" or the "right eye of the true Dharma."
Buddha's joy upon his great awakening was so immense that he continued sitting in zazen on the spot for over ten days.
Initially, he thought, "Such an experience is impossible for anyone other than me." However, upon reconsidering, he set out on a journey to spread his teachings.
