The Home Insurance Building, built in 1885 and demolished in 1931, was widely considered to be the world’s first skyscraper, and for good reason. Several days before the building opened to the public, William LeBaron Jenney, the building’s architect, took a stroll on the roof. As he looked across the then-diminutive Chicago landscape, he yawned and stretched his arms above his head, unexpectedly bumping something above him. Jenney was not standing near any roof structures at the time.

He extended his hand upward and came into contact with a “transparent, glass-like surface, warm to the touch.” His hand left smoky handprints that quickly disappeared from this mystery surface, and he scratched off some of the material with his fingernail, reporting that it was “dense, but weightless, and ha[d] a pleasant aroma.” When Jenney returned to the roof with several others to verify his claims, he could not locate the mystery surface again.

Jenney did not return to the roof of the Home Insurance Building until five years later, when two stories were added to the building’s original ten stories. He once again searched for the mystery surface, with no luck. Before leaving the roof for what would be the last time, Jenney felt “an odd sensation of being watched.”