GR translation: a legend to be deciphered

[Mike Jing]

V72.34-73.3, P74.13-17   At The White Visitation the walls read ice.
Graffiti of ice the sunless day, glazing the darkening blood brick and
terra cotta as if the house is to be preserved weatherless in some skin of
clear museum plastic, an architectural document, an old-fashioned apparatus
whose use is forgotten. Ice of varying thickness, wavy, blurred, a legend
to be deciphered by lords of the winter, Glacists of the region, and argued
over in their journals.

In what sense is the word "legend" used here? I've always thought it means
"inscription", but the published translation interprets it as "story".