From Self-Development and the Way to Power, by L. W. Rogers (28)

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Still another useful practice is to exercise the imagination, the art
of creating mental pictures with no physical object present. The face
of an absent friend can be called up in the mind and reproduced in
every detail--the color of the eyes and hair, the various moods and
expressions. Or one's childhood home can be recalled and the
imagination made to reconstruct it. The house being complete the
landscape can be reproduced, with the hills, trees and roads. Repeated
practice at "seeing mentally" is of the greatest value in occult
development.