According to the currently available historical sources, did Ledi Sayadaw invent his technique of meditation, or did he learn it in the caves of the Sagaing Hills? Is there enough information to tell which possibility is more likely?
Though there is no definite record who his teacher was, it is said he learned it from someone else when he was in the Monywa region in the side of Lak-pan-taung Mountain. Also there is reference that this is the
Traditional Burmese method. This is mentioned in the VRI and pariyatti.org biography. VRI teachers Vipassana as handed down in the Ledi linage. VRI may be drawing on works by Sayagyi U Ba Khin (E.g. The Clock of Vipassana Has Struck page 71 also makes reference to this.) It the strong belief of this tradition (which I also very much involved and practice) that he learned from a linage handed down from the Sona and Uttara who came as missionaries during King Asoka's time.
The Wikipedia entry (originally sourced from On saints and wizards Ideals of human perfection and power in contemporary Burmese Buddhism by Patrick Pranke page 461) mentions
Ledi Sayadaw learned the technique of Vipassana which had remained being taught in the caves of the Sagaing Hills.
Hence this was not exactly his creation as per biographical references above. But the book The Birth of Insight in in page 7 says otherwise though. So there is no proper or consistent way to determine what exactly is right, though previous case may be right. There are parallel of the technique to some extent in other linages too.
For eight more years he remained there, teaching and continuing his own scholastic endeavors, until 1882 when he moved to Monywa. He was now 36 years old. At that time, Monywa was a small district center on the east bank of the Chindwin River, which was renowned as a place where the teaching method included the entire Tipiṭaka, rather than selected portions only.
To teach Pali to the bhikkhus and sāmaṇeras at Monywa, he came into town during the day, but in the evening he would cross to the west bank of the Chindwin River and spend the nights in meditation in a small vihara (monastery) on the side of Lak-pan-taung Mountain. Although we do not have any definitive information, it seems likely that this was the period when he began practicing Vipassana in the traditional Burmese way: with attention to Ānāpāna (respiration) and vedanā (sensation).
Ledi Sayadaw learned the technique of Vipassana which had remained being taught in the caves of the Sagaing Hills, which was honeycombed with meditation caves and dotted with forest monasteries. For how long we do not know. Verbal accounts state that two monks brought the practice of Vipassana to this area at the time of the Buddha. It is just as likely that prior to the eighteenth century in Burma, as elsewhere in the Theravāda world, it was generally believed that it was no longer possible to attain enlightenment and hence nibbāna through vipassanā or any other means during the present age.
The earliest known challenger to this assumption is that of a monk from the Sagaing Hills in Upper Burma named Waya-zawta whose movement ﬂourished during the reign of Maha-damma-yaza-dipati (r. 1733–1752). A young scholar-monk named Medawi (1728–1816) began writing vipassanā manuals in the vernacular. Couched in the language of abhidhamma, these are the very earliest ‘how-to’ vipassanā books we possess from Burma. Medawi’s earliest manual was completed in 1754. Ledi's lineage comes from this line, whereby his main teacher was King Mindon’s royal minister U Hpo Hlaing (1830–1883), who was notable for his avid interest in western science and eﬀorts to reconcile this new perspective with abhidhamma. This synthetic approach was passed on to his protégé, the scholar-monk, U Nyana, who later became famous as Ledi Sayadaw, arguably the most signiﬁcant promoter of vipassanā in the modern period.