With regard to the five flavors that are used to analogize five levels of the position of the Perfect Teaching, Chih-i cites an allegory from the Nirvāṇa Sūtra:

“In the Snow Mountains, there is a type of grass named ‘enduring humility.’ If a cow eats the grass, it immediately attains ghee.” “The cow is analogous with an ignorant man, and the grass is analogous with the Eightfold Correct Path. [If one] can cultivate the Eightfold Correct Path, [one] instantaneously perceives the Buddha-nature, which is called the attainment of ghee. This is analogous with the Perfect Teaching, with which [one] walks on the wide and straight road and observes that all sentient beings are identical to the characteristic of Nirvāṇa, which can no longer be extinguished.”

By quoting the Nirvāṇa Sūtra, Chih-i intends to say that the bodhisattva of the Perfect Teaching does not need to go through the first four stages of flavor before he can directly arrive at the final stage of ghee. This is an expression of the superiority of the Perfect Teaching. Chih-i affirms that there are four subtleties that constitute the Perfect Teaching and can be drawn from this analogy. (i) The fact that the cow can instantly attain the ghee as truth through eating grass signifies that the conception of truth of the Perfect Teaching is ultimate. Thus, the grass of acquiescence (Jents ‘ao) is the metaphor for the Subtlety of Objects (Ching-miao). (ii) The attainment of liberation as the result of the cow eating grass suggests that the cow is the metaphor for the Subtlety of Knowledge (Chih-miao) that penetrates truth. (iii) The fact that the actualization of liberation is due to the action of eating grass indicates that this action of eating is used as the metaphor for the Subtlety of Practice (Hsing-miao). (iv) Finally, ghee is used as the metaphor for the Subtlety of Positions (Weimiao). (Vol. 2, Page 232)