“I am enough of an artist to draw freely upon my imagination. Imagination is more important than knowledge. Knowledge is limited. Imagination encircles the world.”

Cosmic Religion : With Other Opinions and Aphorisms (1931) by Albert Einstein, p. 97; also in Transformation : Arts, Communication, Environment (1950) by Harry Holtzman, p. 138. This may be an edited version of some nearly identical quotes from the 1929 Viereck interview below.
1930s
Context: I believe in intuition and inspiration. … At times I feel certain I am right while not knowing the reason. When the eclipse of 1919 confirmed my intuition, I was not in the least surprised. In fact I would have been astonished had it turned out otherwise. Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution. It is, strictly speaking, a real factor in scientific research.

1940s, A History of Western Philosophy (1945)

"Quotes", The Educated Imagination (1963), Talk 1: The Motive For Metaphor http://northropfrye-theeducatedimagination.blogspot.ca/2009/08/1-motive-for-metaphor.html
Context: At the level of ordinary consciousness the individual man is the centre of everything, surrounded on all sides by what he isn't. At the level of practical sense, or civilization, there's a human circumference, a little cultivated world with a human shape, fenced off from the jungle and inside the sea and the sky. But in the imagination anything goes that can be imagined, and the limit of the imagination is a totally human world.

Source: The Poet's Diary (1904), p. 158.

Nano Reid (1950)