The slender hardcover volume that I have is the centennial edition published by Cosimo Classics. The text looks like a photocopy of the original text from 1907 when William Walker Atkinson published it under the pseudonym "Yogi Ramacharaka." As such the text is a bit smudged in places and a bit faded in others, but not so much that the reader really misses anything. Amazon has several different editions listed, one by the Nabu Press and another by Kessinger Publishing, but I believe they are all essentially the same text.
Although the blurb on the back cover states that the aphorisms are "culled from the Upanishads," that is only technically correct since "Upanishads" refers to a genre of Hindu literature and not just to the traditional works written before the current era. At any rate I was interested to note that quite a few of the aphorisms are from "Yogavasishtha" which Georg Feuerstein in his "Shambhala Encyclopedia of Yoga" identifies as "a didactic poetic work" from the ninth to the thirteenth century CE. Other quotations are from the "Upadesha-Sahasri" written by Shankara (?788-822 CE), while still others are from "Miscellaneous."
The aphorisms are presented in fourteen parts from "Part I The Threshold," "Part II The Absolute," "Part III The Real Self," and so on to "Part XIV Liberation." Here are some examples of the wisdom within:
"Said Prajapati: whence does come this fear! With the thought, 'why did I fear?' disappeareth all fear; for, fear comes of duality." --Brhadaranyakopanishad (p. 43)
Note the archaic expression and that " Brhadaranyakopanishad" is the "Brihadaranyaka Upanishad" in the modern parlance.
"A mere cover of bark satisfies one; but another seeks satisfaction in wealth and luxury. The feeling, however, is the same in either case, and the difference is really no difference at all. He, indeed, is the miserable man of poverty who has in him the most insatiable desire. The mind being all contentment, what can make the rich or the poor?" --Vairagyasataka (p. 53)
The "Vairagya Satakam" ("One Hundred Verses on Renunciation") was written by the poet Bhartrihari (seventh century, CE) within the Advaita Vedanta tradition. By the way, surveys and polls in modern times have shown again and again that beyond a comfortable subsistence more wealth does not increase human happiness.
Another verse from Bhartrihari is "There is the greatest misery in hope; in hopelessness is the height of bliss." (p. 53)
"If the wise man of the world who carefully picks holes in the character of others, would but expend the same skill on himself, what could prevent him from breaking through the bonds of Ignorance. (p. 54)
This aphorism is attributed to "Smrti" ("Smriti") which means "that which is remembered." The term refers to a vast Hindu literature in religion and law.
"That patience which would empty the ocean drop by drop, at the tip of a straw of the Kusa-grass, will, untiringly sustained, establish control over the mind. --Gaudapadacharya (p. 59)
According to Feuerstein, Gaudapada Acharya was the teacher of Govinda who was Shankara's preceptor. He was an advocate of Advaita Vedanta, which I should mention is one of the six orthodox philosophies of India and one that I greatly admire. Uh...by the way, I hope it wouldn't take that long--that is to establish control over the mind!
"The emptying of the mind of the whole of its illusion is the true rechaka [breathing out]...; the full realization of the idea 'I am Spirit' is the true puraka [breathing in]...; and the firm steady sustenance of the mind on this conviction is the true Kumbhaka [the breath held]. This is the true Pranayama of the enlightened; fools find it only in torturing the nose." --Aparokshanubhuti (p. 64)
According to Feuerstein, "Aparokshanubhuti" ("Unmediated Realization") is a work attributed to Shankara. The "realization" is that of the Self (as Atman) as synonymous with Brahman.
"The traveler with his mind firmly fixed only on the goal he is approaching, never feels the motion of his legs along the road he treads; act thus in all you do." --Yogavasishtha (p. 82)
(Note: My book, "Yoga: Sacred and Profane (Beyond Hatha Yoga)" is now available at Amazon.)
Yoga: Sacred and Profane: (Beyond Hatha Yoga)