The first Christian missionaries in China were not the 16th-century Jesuits or the 19th-century Protestants.  They were preceded--by over a millenium--by monks of the Church of the East, commonly but erroneously known as the Nestorian church.  Traveling from the Near East over the Silk Road, a monk named Alopen and several companions reached Tang China in the year 630.  They were able to grow a substantial church, one which gained the admiration of the emperor and which flourished for several centuries.  Christianity became known in Chinese as the Luminous Religion of Daquin (the Roman Empire).  There was significant interaction with indigenous Chinese religions, especially Taoism. 

This is reflected in the text of the so-called Nestorian Stele.  Erected in 781, it was written by Jingjing, a monk whose Syriac name was Adam.  The text is in both Chinese and Syriac and contains information about the structure of the Church of the East in China and its teachings.  The  excerpt below is found in Not of This World:  A Treasury of Christian Mysticism, James S Cutsinger, ed, World Wisdom 2003, pp126-127.

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In the beginning was the natural constant, the true stillness of the Origin, and the primordial void of the Most High.  The Spirit of the void emerged as the Most High Lord, moving in mysterious ways to enlighten the holy ones.  He is Ye Su, my True Lord of the Void, who embodies the three subtle and wondrous bodies, and who was condemned to the cross so that the people of the four directions might be saved.

He beat up the primordial winds, and the two vapors were created.  He differentiated the gray emptiness and opened up the sky and the earth.  He set the sun and moon on their course, and day and night came into being.  He crafted the myriad things and created the first people.  He gave to them the original nature of goodness and appointed them as guardians of all creation.  Their minds were empty, they were content, and their hearts were simple and innocent.  Originally they had no desire, but under the influence of Satan, they abandoned their pure and simple goodness for the glitter and the gold.  Falling into the trap of death and lies, they became embroiled in the threee hundred and sixty-five forms of sin.  In doing so, they have woven the web of retribution and have bound themselves inside it.  Some believe in the material origin of things, some have sunk into chaotic ways, some think that they can receive blessings simply by reciting prayers, and some have abandoned kindness for treachery.  Despite their intelligence and their passionate pleas, they have gone nowhere.  Forced into the overturning wheel of fire, they are burned and obliterated.  Having lost their way for eons, they can no longer return.

Therefore my Lord Ye Su, the One emanating in three subtle bodies, hid His true power, became a human, and came on behalf of the Lord of Heaven to preach the good teachings.  A Virgin gave birth to the Sacred in a dwelling in the Western Empire.  The message was given to the Persians, who saw and followed the bright light to offer Him gifts.  The twenty-four holy ones have given us the teachings, and Heaven has decreed that the new religion of the Three-in-One Purity that cannot be spoken of should now be proclaimed.  These teachings can restore goodness to sincere believers, deliver those living within the boundaries of the eight territories, refine the dust and transform it into truth, reveal the gate of the three constants, lead us to life, and destroy death.  The teachings of the Religion of Light are like the resplendent sun:  they have the power to dissolve the dark realm and destroy evil forever.

The Lord set afloat the raft of salvation and compassion so that we might use it to ascend to the palace of light and be united with the Spirit.  He carried out the work of deliverance, and when the task was completed, He ascended to immortality in broad daylight.  He left twenty-seven books of scriptures to inspire our spirit, He revealed the workings of the Origin, and He gave to us the method of purification by water.  Thus we purify our hearts and return to the simple and natural Way of the truth.  This truth cannot be named, but its power surpasses all expectations.  When forced to give it a name, we call it the Religion of Light.  As with the Way, that which is sacred is not sacred unless it is highly sacred, and that which is the Way is not the Way unless it is the Great Way.

Today's feast of the Transfiguration, somewhat ignored by the Western churches, is of paramount importance in the Orthodox and Oriental churches.  This is because it is closely related to the doctrine of theosis, which lies at the heart of Eastern Christian spirituality.  On Mt Tabor, Jesus manifested the Uncreated Light, which Orthodox spiritual teachers maintain is God's divinity made visible to human eyes.  The Uncreated Light can also be manifested by Christians who have made substantial progress along the path to deification.  Probably the best-known example of this is St Seraphim of Sarov, the 19th-century starets whose illumination was described by his disciple Motovilov.

The significance of the Light during the actual Transfiguration is described in a sermon excerpted below by St Gregory Palamas (1296-1359).  Palamas, a monk of Mt Athos, defended the Athonite tradition of hesychasm against Barlaam of Calabria, a Greek from southern Italy whose theology was influenced by Roman Catholic scholasticism.  Barlaam held that the light experienced by Palamas and his brother monks was a created thing, if indeed it was not a product of self-delusion.  After a series of fiercely-contested theological debates, the Orthodox Church agreed with Palamas, and his opinions became part of official Orthodox teaching.  Palamas eventually became Archbishop of Thessalonica, where he delivered the following sermon. 

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Thus, the Light of the Transfiguration of the Lord  is not something that comes to be and then vanishes, nor is it subject to the sensory faculties, although it was contemplated by corporeal eyes for a short while upon an unconsequential mountaintop.  But the initiates of the mystery, the disciples of the Lord, at this time passed beyond mere flesh into spirit through a transformation of their senses, effectualized within them by the Spirit, and in such a way that they beheld what, and to what extent, the Divine Spirit had wrought blessedness in them to behold the Ineffable Light...

...That same Inscrutable Light shone and was mysteriously manifest to the apostles and the foremost of the Prophets at that moment, when the Lord was praying.  This shows that what brought forth this blessed sight was prayer, and that the radiance occurred and was manifest by uniting the mind with God, and that it is granted to all who, with constant exercise in efforts of virtue and prayer, strive with their mind towards God.  True beauty, essentially, can be contemplated only with a purified mind.  To gaze upon its luminance assumes a sort of participation in it, as though some bright ray etches itself upon the face...

...We believe that at the Transfiguration He manifested not some other sort of light, but only that which was concealed beneath His fleshly exterior.  This Light was the Light of the Divine Nature, and as such, it was Uncreated and Divine.  So also, in the teachings of the Fathers, Jesus Christ was transfigured on the Mount, not taking upon Himself something new nor being changed into something new, nor something which formerly He did not possess.  Rather, it was to show His disciples that which He already was, opening their eyes and bringing them from blindness to sight...

...Thus, this Light is not a light of the senses, and those contemplating it do not simply see with sensual eyes, but rather they are changed by the power of the Divine spirit.  They were transformed, and only in this way did they see the transformation taking place amidst the very assumption of our perishability, with the deification through union with the Word of God in place of this.