Let's quote the cellar master's notes, "Hot weather lasting from 1st March until the harvest. An excessively hot summer. Without rain. Vines flowered 20th April. Grapes changed colour 21st June. An extremely early and very abundant crop." (Picking began 17th August, finishing 12th September)
Up till then, the harvest had never begun so early in the year (August 17th), and it has never done so since! 1893 was also the biggest crop ever recorded at Château Margaux ! Even during the 1980s, we never harvested such a huge volume. As the cellar master mentioned, the picking had to be interrupted for six days because there were not enough vats.
Château Margaux 1893 is a remarkable wine, which was considered to be the best of the century (of the 19th, of course). Still today, this wine displays quite amazing power and freshness. How did they manage to do that ? Producing such a huge quantity and making such fine quality is a great mystery, and we do not have enough information to explain it.