Eight Secret Song (歌訣八) from the The Thirty-Six Songs of Baguazhang (八卦掌三十六歌)

歌訣八

走時周身莫動搖，
全憑膝下兩相交。
底盤雖講平膝胯，
中盤也要下腿腰。

"When walking, the entire body remains stable.
The whole relies on the knees intersecting.
Although the lower section concerns the leveling of knees, waist and thighs,
The middle section is also dependent on the legs and waist."

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"

Yáng Chéngfǔ (楊澄甫) performing Fist under Elbow (肘底看捶)

The Song of the Arms (臂) in the Nine Songs of Xing Yi Quan (形意拳九歌) by Jiāng Róngqiáo (薑容樵)

臂
左臂前伸，
右臂在肋，
似曲不曲，
似直不直，
過曲不遠，
過直少力。
薑容樵

"The left arm stretches forward.
The right arm is by the ribs.
They seem bent but are not bent.
They seem straight but are not straight.
Bend too much and there is not enough reach.
Make it too straight and there is not enough strength."

From the book Xing Yi Mother Fists (形意母拳), by Jiāng Róngqiáo (薑容樵), based on the translation by Joseph Crandall

The Entering and Support of Yin and Yang (陰陽入扶論) from the Chang Family Comprehensive Theory of Martial Arts (萇氏武技全書)

陰陽入扶論

練形不外陰陽，陰陽不明從何練起，督脈統領諸陽經，任脈統領諸陰經，故背為陽，腹為陰，二經下交會陰，上會齦交。
俯式為陰勢，卻是入陽氣，益督脈，領諸陽經之氣，盡歸於上之前也；仰式為陽式，卻是入陰氣，益任脈，領諸陰經之氣，盡歸於上之後也。

萇乃周

"Training the physical form is nothing more than yin and yang. If we fail to understand yin and yang, how would one know where to begin our training? The governing vessel (du mai) commands all of the yang channels. The controlling vessel (ren mai) commands all of the yin channels. This is the reason why the back is yang, and the belly is yin. The two channels intersect below at the Perineum (hui yin, CV-1) and above at the Gum Intersection (duan jiao, GV-28).
To look down is a Yin posture, it allows the Yang chi to enter. It benefits the governing vessel. It concentrates the chi of all yang channels, which finishes at the upper front aspect of the body. To look up is a Yang posture and allows the Yin chi to enter. It benefits the controlling vessel, leads the chi of all Yin channels, which finishes at the upper rear aspect of the body."

From the book Chang Family Comprehensive Theory of Martial Arts (萇氏武技全書), by Cháng Nǎizhōu (萇乃周), based on the translations by Douglas Wile in "T'Ai Chi's Ancestors: The Making of an Internal Art" and Marnix Wells in "Scholar Boxer: Chang Naizhou's Theory Of Internal Martial Arts And The Evolution of Tàijíquán"

Chapter 47 (四十七) from the Dào​dé​jīng (道德經)Capítulo 47 (四十七) do Dào​dé​jīng (道德經)

四十七

不出戶知天下。
不闚牖見天道。
其出彌遠，
其知彌少。
是以聖人
不行而知。
不見而明。
不為而成。

老子

"Without going outside his door, one understands all that takes place under the sky;
without looking out from his window, one sees the Dao of Heaven.
The farther that one goes out, the less he knows.
Therefore the sages got their knowledge without travelling;
gave their names to things without seeing them;
and accomplished their ends without any purpose of doing so."

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

"Sem sair da porta
Pode-se conhecer o mundo
Sem ver através da janela
Pode-se conhecer o Caminho do céu
Quanto mais longe saímos
Tanto menos conhecemos
Por isso, o Homem Sagrado
Conhece sem caminhar
Reconhece sem ver
Realiza sem agir"

Tradução de Wǔ Rǔqīng (武汝清)

The Secret of Withdraw and Release (撤放密訣)

撤放密訣

一曰擎。擎起彼身借彼力。（中有靈字）
二曰引。引到身前勁始蓄。（中有斂字）
三曰鬆。鬆開我勁勿使屈。（中有靜字）
四曰放。放時腰腳認端的。（中有整字）

李亦畬

"First saying: Raise. Start by raising the hand (deflect) and borrow the force of the opponent’s body. Within there is the word of agility.
Second saying: Pull. Lead the frontal force near one's own body and start storing it. Within there is the word of collecting.
Third saying: Loose. To release the force, relax without bending. Within there is the word of calmness.
Fourth saying: Release. At the time of releasing, the waist and the feet must be accurately coordinated. Within there is the word of precision."

By Lǐ Yìyú (李亦畬), based on the translation by by Yang Jwing Ming (楊俊敏) presented in the book Tai Chi Secrets of the Wu/Li Style (太極拳武李氏先哲秘要) and various translations on the internet