Sigma Xi, the Scientific Research Society.

Sigma Xi, the Scientific Research Society, was formed in 1886 at Cornell University as an honor society for science and engineering; the original founders of Sigma Xi were members of the Sibley College of Mechanical Engineering at the university. Moving beyond the Society's early intention of fostering companionship, Sigma Xi has since evolved to offer the sciences a strong, unified voice in support of scientific advancement and achievement.

From the description of Sigma Xi, The Scientific Research Society records, 1928-2003 [manuscript] (North Carolina State University). WorldCat record id: 537697053

...