These classics about controlled intercourse are available here. You can read them online by following the links, or, in some cases, download and print them out:
For those who enjoy historical tidbits about others who wrestled with how to channel their sexual energy upward, "Right Marital Living" is a colorful piece with an aura of tragedy. Its author, Ida Craddock, was a Philadelphian born in 1857, heavily influenced by Theosophical Society works and other mystical writings, some of which were just appearing from the Far East in translation.
Her essays on sacred sexuality and natural birth control drew fire from a man named Anthony Comstock and his self-appointed "Society for the Suppression of Vice," who had her writings declared pornographic. She was arrested twice. In 1902, on the day she was to be sentenced the second time, she committed suicide leaving behind an outraged letter to the public. Her death brought disgrace to the "Society for the Suppression of Vice," which disbanded not long afterward.