Full Idea
Not every a priori cognition must be called transcendental, but only that by means of which we cognize that, and how certain representations (intuitions or concepts) are applied entirely a priori, or are possible.
Gist of Idea
Transcendental cognition is that a priori thought which shows how the a priori is applicable or possible
Source
Immanuel Kant (Critique of Pure Reason [1781], B80/A56)
Book Reference
Kant,Immanuel: 'Critique of Pure Reason', ed/tr. Guyer,P /Wood,A W [CUO 1998], p.196
A Reaction
Kant really wasn't good at expressing himself. I would describe this as either explanation, or as meta-thought.
Related Idea
Idea 624 Absolute thinking is the thinking of thinking [Aristotle]