3 volumes, 8vo (222 x 140 mm). Half-titles in second and third volumes as usual; 5 engraved portraits (Count Cagliostro plate remargined and reinserted on a new leaf, occasional light spotting, dampstaining in vol.I to frontispiece, title-page gutter, and a couple subsequent leaves near top edge.) Early 20th-century half red morocco gilt, spines in 6 compartments with 5 raised bands, gilt-lettering in 3, others gilt ruled, top edges gilt, others uncut, stamp-signed by J. Larkins (light rubbing to fore-corners, some darkening near head on vol.I).

FIRST EDITION. Memoirs of Extraordinary Popular Delusions is considered to be one of the earliest studies of crowd psychology ever printed, with its author devoting individual chapters to debunking some of the most popular myths of the day, including alchemy, fortune-telling, prophecies, witch manias, tulipomania, and the infamous Mississippi Scheme. The work has proven especially popular in finance circles, with financier Bernard Baruch famously crediting the lessons learned from reading MacKay's book to his decision to sell all of his stock just before the 1929 Wall Street crash.