First there was one: a toy horse discarded in a field on the side of Old Sudbury Road. Jimmy Pingeon and Elizabeth Graver, who own the pasture and live next door, told the Boston Globe in 2015 that the prop was leftover from a Headless Horseman display they had set up for Halloween. They thought a kid might find it and play it with, but they never imagined the horse would inspire a local landmark that lives on more than a decade later. After the first equine seed was planted, other horse toys began showing up randomly in the area....