September 19 Thursday – The Clemens party spent the day looking around Milan.
September 20 Friday – Sam (and probably the ladies) went to see Da Vinci’s “Last Supper” in the refectory of the monastery of Santa Maria delle Grazie in Milan. “If there is anything worse than the original, it is the 15 or 20 copies in oil & water”. They also visited the “great picture gallery” (Brera).
“There are artists in Arkansas to-day who would not have had to paint signs for a living if they had had the luck to live in the time of the old masters”.
September 21 Saturday – Sam’s notebook:
The Italians all seem to go to work before daylight—& all in couples, singing tenor & bass or alto duet —all got strong voices & many good ones—don’t sing simple airs but starchy opera stuff—they wake you up and keep you awake. The Milan clocks are not useful. This morning one struck 2, another 3, another 1, another 2, two others 3—all this occupied 10 minutes—so I got up & looked at my watch—correct time 4.15. 15 minutes later, the procession of striking began again.

From page 266 The Life of Mark Twain - The Middle Years 1871-1891:

They left Turin by rail the morning of September 18 and arrived four hours later in Milan, They registered at the venerable Hotel de Ville, which, Sam complained, swarmed “with mice and fleas, and if the rest of the world were destroyed it could furnish dirt enough to start another one.” Nor was its table d’hôte tolerable: “The food would create an insurrection in a poorhouse.” But its “excellent reputation still keeps its dreary rooms crowded with travelers.” They spent most of a week in the city “in the vast and beautiful” newly opened shopping mall, Galleria Vittorio Emanuele II, though they also tarried “an impressive hour in the noble cathedral,” which Sam had toured during the Quaker City excursion almost twelve years earlier.