The Clemens party, including Livy, Susy, Clara, Clara Spaulding and Rosina Hay, the nursemaid, sailed for Hamburg on the S.S. Holsatia on 11 April 1878. They arrived in Hamburg 25 April 1878.

April 25, 1878: Thursday – The Clemens family arrived at Hamburg and took rooms at the Crown Prince Hotel. Sam insisted that the family rest in Hamburg a week. They stayed five days. Livy wrote her mother on Apr. 26 that Hamburg “was the finest city I was ever in”.

Twain, in a letter to William Dean Howell, describes his journey from Hamburg to Heidelberg as "...fooling along, 4 hours per day by rail, with a courier, spending the other 20 in hotels whose enormous bedchambers & private parlors are an overpowering marvel to me." He is not particularly detailed about his itinerary, however. The letter was posted from Frankfurt on the Main, 4 May 1878, near the end of the journey. He does mention that the "Day before yesterday" they were in Cassel.

The Clemens party took rooms at the Hotel Schloss in Heidelberg from May 6 to July 23 of 1878.

From Chapter 2 of A Tramp Abroad: At Heidelberg

The Clemens party left Heidelberg on 23 July 1878 and proceeded to Baden-Baden, where they would meet Joe Twichell on 1 August.

Twain hired the portier of the Schloss Hotel, Georg Burk, as courier for $55/month and expenses and departed Heildelberg by train for Baden.

There are two possible railway lines that could have been used for this trip: