Definitions

A central concept within epistemology is perception.

The term is vaguely defined within psychology. My suggestion, below, is mainly based on some textbooks [Ciccarelli, Goldstein, Gross, Lilienfeld, Schacter]:

Perception implies that the brain receives simultaneous signals from one sensory organ. The brain compares these with earlier memories and keeps in memory what it estimates as important, useable, new or altered.

The perception is composed, or synthesised, by several components, e.g. by its duration in time, movement, strength, and dangerousness. The brain creates the experience that it is one unit that is perceived.

A perception hence implies a concept formed due to contiguity in time.

Simultaneous perception through several sensory organs, or multimodal perception, e.g. of a large animal that looks like, smells like, and sounds like a horse form a strong belief about the credibility of the perception.

Everybody agrees that a at least great deal of what we judge as reliable arguments ultimately are created through perception.

Aristotle about perception

Within philosophy it is quite common to find misconceptions and erroneous citations.

One of Aristotle's two books that he together called "Analytics" was long after his death renamed to "Prior Analytics" [Ross]. This has led to the misconception that he thought that knowledge could be created a priori. He did not believe that.

The term "universal" implies a concept, a generalisation:

Thus from perception there comes memory ... and from memory ... experience ... . And from experience ... there comes a principle of skill or of understanding ... .

Thus it is clear that it is necessary for us to become familiar with the primitives by induction; for perception too instils the universal in this way.

Aristotle - Posterior Analytics 2, 100a5.

Aristotle hence claimed that the starting points or premises in the ultimate reasoning (that he called primitives) are based on perception.

Observation

The term observation at this website implies "focused perception", where focusing is caused e.g. by earlier experience, news value or by some requirement.

Ultimately

That knowledge is ultimately created through perception implies that knowledge is created through perception, through reasoning that starts from perception or through reasoning that starts from earlier conclusions from reasoning (and hence from perception).