"Euler left Basel on 5 April 1727. He travelled down the Rhine by boat, crossed the German states by post wagon, then by boat from Lübeck arriving in St Petersburg on 17 May 1727."
Still inconclusive, but given that we know this, I would say chances are non-zero that the sources this was derived from spell out where that ship made stops.
One could also look at his journeys from Leningrad to Berlin and, years later, back, but both were after his publication on the 7 bridges problem.
Yes, he was in Switzerland, in Basel. Googled a bit. http://www-groups.dcs.st-and.ac.uk/history/Biographies/Euler...:
"Euler left Basel on 5 April 1727. He travelled down the Rhine by boat, crossed the German states by post wagon, then by boat from Lübeck arriving in St Petersburg on 17 May 1727."
Still inconclusive, but given that we know this, I would say chances are non-zero that the sources this was derived from spell out where that ship made stops.
One could also look at his journeys from Leningrad to Berlin and, years later, back, but both were after his publication on the 7 bridges problem.