From Philip Jenkins' "The Lost History of Christianity":
Around the time this memorial was erected, in 782, the Indian Buddhist missionary Prajna arrived in the Chinese imperial capital of Chang’an, but was unable to translate the Sanskrit sutras he had brought with him into either Chinese or any other familiar tongue. In such a plight, what could the hapless missionary do but seek Christian help? He duly consulted the bishop named Adam, whose name headed the list on the Nestorian monument. Adam had already translated parts of the Bible into Chinese, and the two probably shared a knowledge of Persian. Together, Buddhist and Nestorian scholars worked amiably together for some years to translate seven copious volumes of Buddhist wisdom. Probably, Adam did this as much from intellectual curiosity as from ecumenical goodwill, and we can only guess about the conversations that would have ensued: So, what exactly is this “bodhisattva” we hear so much about? Do you really care more about relieving suffering than atoning for sin? And your monks meditate like ours do? Scholars still speculate whether Adam infiltrated Christian concepts into the translated sutras, consciously or otherwise.
Adam’s efforts bore fruit far beyond China. Other residents of Chang’an at this time included Japanese monks who took these very translations back with them to their homeland. In Japan, these works became the founding texts of the two great Buddhist schools—respectively, Shingon and Tendai; and all the famous Buddhist movements of later Japanese history, including Zen and Pure Land, can be traced to one of those two schools.