3 volumes, 8vo (222 x 133 mm). Half-titles in second and third volumes; 5 engraved portraits (some minor offsetting, very light spotting throughout.) 20th-century half crushed green morocco, top edges gilt, others uncut (very light rubbing). Provenance: Armorial bookplate.

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.