I hope this is a reasonable place to ask this question, at least until an art history StackExchange shows up. My memory is hazy about this but I seem to remember a René Magritte painting that depicts a horse-headed woman, facing right, in front of a stone window or sill, with hills in the distance. The overall painting might have had a blue or grey tint. The painting is not "Pure Reason" (1948) or "The Fine Idea" (1964), both of which feature similar horse-headed ladies, but no sill.
For bonus points, I'd love to know more about that painting -- where it is currently, when was it painted, and what does it mean.