"One breath" (Yīxī) refers to one inhalation and one exhalation.

The Remnants of the Dharma Sea (Fǎhǎi Yízhū) states: "Regulate and harmonize eighty-one breaths." A note explains: "One inhalation and one exhalation constitute one breath."
The Essential Guide to Vitality and Destiny (Xìngmìng Guīzhǐ·Hēngjí) says: "As long as one breath remains, life can be restored. If one understands the method of adding oil to the lamp, a dying flame can be reignited."
The Book of Master Guanyin (Guānyǐnzǐ) states: "When not a single breath remains, the Tao will align with you."
✨ Recommended Taoist Talismans
Discover powerful talismans for your spiritual journey