Wú style Tai Chi Sword (吳式太極劍) by Mǎ Yuèliáng (馬岳樑)

The Secret of Random Ring (亂環訣) by Yáng​ Bān​hóu​ (楊班侯)

亂環訣

亂環術法最難通，上下隨合妙無窮。
陷敵深入亂環內，四兩千斤招法成。
手腳齊進橫豎找，掌中亂環落不空。
欲知環中法何在，發落點對即成功。

楊班侯

"It is the hardest to understand the techniques of random ring. The top and the bottom follow each other harmoniously, its marvelousness is unlimited. Trap the enemy deeply into the random ring and use four ounces to repel a thousand pounds, the techniques are then completed. The hands and feet enter together and search for the opportunity in the horizontal and vertical movements. The attack of the random ring in the palms will not be empty. If one wishes to know what are the techniques used in the ring, emitting, falling, pointing and matching, then the success is immediate."

Based on the translation by Yang Jwing Ming (楊俊敏) presented in the book Tai Chi Secrets of the Yang Style (太極拳楊氏先哲秘要)

Chinese Longsword

Chinese Longsword's explicit mission is to "promote and preserve martial arts ancient wisdoms and knowledge" and "translate ancient Chinese manuals to share it with the world", a mission that it has been accomplishing rather well. The selection of the texts available is very interesting: texts that are not easily reachable for the western practicioner (although some of them can be found in chinese on the internet), in translations that are modern and accessible. The rarity of some of the weapons adressed, like whip (鞭) or shield and wolf brush (牌與狼筅), make the translations already interesting from a historical perspective.
The texts are some centuries old, and refer mostly to shaolin or military manuals. At the time the distinction between internal and external martial arts was starting to brew. For example, the "Boxing Treatise"(拳經) from the "New and effective methods in military science" (紀效新書) by Qī​ Jìguāng (戚繼光) is more or less contemporary to the "Sword Treatise" (劍經) translated by Chinese Longsword, it is also arguably one of the first to adress internal aspects of martial arts.
Even if these are mostly "external" manuals, if one understands the evolution of the internal martial arts, the interest is immediate.

As a note of caution for those looking for ancient sword techniques, the "Sword Treatise" (劍經) is mostly about the staff, as it is seen as the source of techniques for other weapons.

Excerpt from Knowledge rambling in the North (知北遊) in Zhuāng zi (莊子)

大馬之捶鉤者，年八十矣，而不失豪芒。大馬曰：“子巧與？有道與？”曰：“臣有守也。臣之年二十而好捶鉤，於物無視也，非鉤無察也。是用之者，假不用者也以長得其用，而況乎無不用者乎！物孰不資焉？”

莊子

"The forger of swords for the Minister of War had reached the age of eighty, and had not lost a hair's-breadth of his ability. The Minister said to him, 'You are indeed skilful, Sir. Have you any method that makes you so?' The man said, 'Your servant has (always) kept to his work. When I was twenty, I was fond of forging swords. I looked at nothing else. I paid no attention to anything but swords. By my constant practice of it, I came to be able to do the work without any thought of what I was doing. By length of time one acquires ability at any art; and how much more one who is ever at work on it! What is there which does not depend on this, and succeed by it?'"

Unless noted otherwise, all quotations of classical texts and accompanying translations come from the Chinese Text Project

Third Secret Song (歌訣三) from the The Thirty-Six Songs of Baguazhang (八卦掌三十六歌)

歌訣三

步彎腳直向前伸，
形如推磨一般真。
屈膝隨胯腰扭足，
眼到三面不搖身。

"The curved step and straight foot extend forward,
The form is as if it was truly pushing a millstone.
Bend knees, the hips follow; the waist twists the feet,
The eyes watch the three surfaces (the surroundings), the body does not change."

Based on the translations by Yang Jwing Ming (楊俊敏) and Liang Shou You (梁守渝) in "Baguazhang - Theory and Applications" (峨嵋八卦掌) and by Frank Allen and Tina Chunna Zhang in "The Whirling Circles of Ba Gua Zhang"