Perhaps the most well known schools of Mahāyāna Buddhism is the Zen tradition.
Japanese "Zen", the Vietnamese "Thien", and the Korean "Son" originate from the Chinese "Ch'an" which in turn is a
continuation of the Indian "Dhyāna" tradition. Zen's description as "direct transmission outside the sutras" comes from
China. Then the various newly imported Buddhist schools, vying for acceptance and support, based
their claims of authenticity on the authenticity of their doctrinal texts - translations of sanksrit Buddhist texts.
Not relying on doctrinal texts, Zen's claim to legitimacy was based upon of a "direct transmission outside the sutras". By presenting a
transmission lineage of twenty-eight Indian Patriarchs originating with Śākyamuni Buddha it's authenticity as a legitimate Buddhist school was
slowly accepted. Shunning intellectual discussions, Zen expressed it's nature with spontaneous, ostensibly nonsensical, expressions of
the enlightend mind (kōans) which under the appropriate circumstances brought numerous monks, nuns and laypeople to a deep enlightenment.
By the 8th century Zen had won the favour of the ruling Emperors whose personal Zen teachers were designated
as "Kokushi" (j.) or "National Master". Many important masters however avoided notoriety and as a result the mainstream
of Zen existed outside of the easily accesible towns. Because of the remoteness of most Zen monasteries, Zen survived the
buddhist persecution by the Tang Emperor Wuzong in the year 845 CE relatively intact.
Later Zen took root in Vietnam, Korea and Japan where Dharma descendents still preserve this "direct transmission outside the sutras".
Today, especially in the Rinzai school, the kōans originating from old China are used to goad practitioneers into an enlightenment experience.
The pages linked below outline, in detail, the original Indian and Chinese transmission lineages of these old masters as well as the subsequent
transmission lineages to Japan, Korea, and Vietnam.