From The Hindu Pantheon, by Edward Moor  (Public Domain Image)
Hatha Yoga Pradipika
tr. by Pancham Sinh
Possibly the oldest extant text about Hatha Yoga, The Hatha Yoga Pradipika was written about the 15th century CE, by Swami Swatmarama, a disciple of Swami Goraknath.
PRODUCTION NOTES: This edition incorporates the text of the 1914 Pancham Sinh translation and Devanagari and romanization of the Sanskrit text. The Sanskrit was derived from an ITRANS file from the Internet. The versification does not match up precisely with the Sanskrit text in the book, particularly in Chapter III. Therefore, I've attempted to match up the ITRANS verses with the verses in the book based on my limited reading knowledge of Sanskrit. This embedded ITRANS converter is still experimental: this book was essentially a pilot project for the feature. I welcome feedback about errors in the conversion of the ITRANS Sanskrit text to Unicode.
Note that the Firefox browser has long-standing and still uncorrected problems displaying Unicode Devanagari, e.g. 'i' is displayed after the consonant, instead of preceding it. This is a known problem with Firefox and there is nothing we can do about it.--JBH