I'm writing historical fiction set in 1870 (June, some weeks before the outbreak of the Franco-Prussian war) in which some of the protagonists are traveling by train across Europe, from Calais to Vienna.
The feasibility of this journey is clear, and I even have a railway map.
Okay, that's nine years earlier, so it doesn't show e.g. the Calais to Boulogne link which was only operational in spring 1870, but it seems to show the links relevant to this journey; looks like the shortest route is Calais - Douai - Liège - Cologne - Koblenz - Mainz - Darmstadt, then either Nuremberg or Stuttgart.
Overall distance is not trivial to reckon exactly. Google says the driving distance from Calais to Vienna nowadays is 1303 km, 810 miles. That's plotting the shortest distance on today's road network, which of course is not a perfectly straight line. But the routes on the above rail map look by eyeball estimate significantly less straight. How much less? Don't know. At a guess, maybe rounding up to 900 miles.
How fast are trains at this time? That's also not trivial to get exact numbers for; most of the results for historical train speeds, talk about maximum momentary velocity achievable in a demo, which is very different from average speed in normal operation. But there seems to be something of a consensus that 20-30 mph was a realistic figure. To take into account time spent stopping at stations on the way, say the lower end of that range is a reasonable ballpark figure, 20 mph, so the 900 mile journey would take 45 hours total. If anyone has more exact figures, I would appreciate them!
The thing I am most unclear about is how the timetabling works. A search for actual train timetables for Europe in the late nineteenth century, has found everything except actual train timetables!
The simplest scenario would be if you could get on a train at Calais, spend forty-five hours occupying yourself brushing up your German or talking to fellow passengers, and get off at Vienna, but did it work like that? Probably there are breaks along the way to change trains, but how many and how long? Did the trains run 24x7, or would there be times when one train drops you off in a city at 1 a.m. and the next one does not depart until 7 a.m.?
One thing I have found evidence for is that the day of the week doesn't matter much
When excursion trains first appeared, it was common practice to run them on Sundays. Sunday observance affected the provision of railway services from the start and there was a conflict between the prompting of conscience and the pressing claims for business efficiency. The Sunday timetable, as the system developed in the 1840s and 1850s, came to differ widely from one railway to another but two generalisations can be made. First, the Post Office was empowered to compel railways to carry mail at any time it appointed; and since it had both to deliver and collect letters on Sundays it insisted on the provision of a good many Sunday mail trains. This was uneconomic for the railway companies and so nearly all mail trains also carried passengers. Secondly, on all British railways the Sunday service was very much less liberal than that offered on weekdays unlike continental Europe where there was very little difference. RichardJohnBR
So Sunday travel in Britain is complicated, but on the Continent, according to the above, was not a problem. But I have not been able to find anything yet about the influence of time of day.