首楞嚴義疏注經 2.626

2.626

想謂取像，想像不實，從虛妄有，故以說酢水生、思崖酸起為喻。因說想酸，因思想峻，故有水酸。以想喻想，近取譬耳。

Conception means grasping images; thinking and imagining are not real, existing out of falsity and delusion; therefore speaking of sour [plums] causing water to arise, and thinking of a cliff causing sourness to arise, are taken as metaphors. Because of speaking, one conceives sourness; because of thinking, one conceives danger; hence water and sourness arise. Using thought to illustrate thought is drawing an analogy from what is close at hand.