Чжу Си
The idea that there is a heavier fraction of "qi" seems to have originated with this passage. Similar ideas show up in the writing of Song dynasty philosopher, particularly Zhu Xi, and there this kind of "materialized lifebreath" is called "zhí". Zhu Xi uses the idea of "materialized lifebreath" to explain what we today would call the phenotypical nature of a human being as opposed to the genotypical nature of that human being.