https://fontanaeditore.com/en/blogs/ccb ... zen-naikanHistorically, Zen Naikan had various sources within the Rinzai stream, and in China even today we have examples of this dynamic Zen teaching; the word naikan was used expressly by Master Hakuin Ekaku only three centuries ago to define a method of cultivating energy associated with a new concept of dynamic meditation practice suited both to laypeople having an active life in society and to practicing monks.
if so, why is it not commonly taught in the rinzai tradition? i know some rinzai zen teachers but none of them know it.