The c. 350 BCE Neiye 內業 or Inward Training is the oldest Chinese received text describing Daoist breath meditation techniques and qi circulation. After the Guanzi, a political and philosophical compendium, included the Neiye around the 2nd century BCE, it was seldom mentioned by Chinese scholars until the 20th century, when it was reevaluated as a "proto-Daoist" text that clearly influenced the Daode jing, Zhuangzi, and other classics. Neiye traditions also influenced Chinese thought and culture. For instance, it had the first references to cultivating the life forces jing "essence", qi "vital energy", and shen "spirit", which later became a fundamental concept in Daoist Neidan "internal alchemy", as well as the Three Treasures in traditional Chinese medicine.