Sunlight floods the white plaza of the Templo de las Mariposas — Temple of the Butterflies — at the ancient city of Teotihuacán, as a handful of tourists in 1960s clothing explore the intricately carved stone columns while behind them, a great rounded pyramid looms against a vivid blue sky. Edna, whose legs were clearly aching from a full day of climbing ("even though I hate to admit it — guess I'm not as young as I used to be!"), dashed off this breathless postcard to her friend Flo in Milton, Massachusetts, before confessing at the bottom: "Excuse writing but am so weary!" The card is a Vistacolor chrome lithograph by Ammex Asociados of Mexico City, and it carries a 80-centavo Mexican airmail stamp from the 1968 Olympic Games era — a philatelic marker that precisely dates this cheerful travel dispatch to the year Mexico City hosted the Summer Olympics.