I heard this anecdote in high-school without any specific names mentioned. The supposed death of the not named emperor would have occured on the occasion of receiving foreign ambassadors from an also un-named European country, who addressed the emperor as a king.
I guess it's just a funny anecdote for high-school students to underline how different the Byzantine emperors considered themselves from other monarchs. However, if the event really has occured, that would be hilarious, so - does anyone know about a Byzantine Emperor who met this, or a similar end?
Hey there, I haven't read anything of this sort in any history of Byzantium I've gone over. There has been a large number of ways that Byzantine Emperors have met their end--my favorite being Nicephorus I, who ended his days with his skull as a Khan's drinking cup--but I've never heard of anything like this. The closest thing I can think of wasn't actually a Byzantine Empire, but was due to the actions of one.
During the reign of Basil II, the Empire won a crushing victory against a long time enemy, the Bulgars. Basil II committed an act of atrocity that would forever earn him the title of "Bulgar Slayer", capturing over 15,000 prisoners and blinding 99 out of every 100. That one remaining was left with one eye, in order to lead the dismembered army back home. Upon their return, Tsar Samuel of Bulgaria was said to collapse from a heart attack at the sight of his army, and died two days later.
This isn't to say that such an anecdote is completely uncharacteristic of the stories we hear of Byzantine Emperors. Perhaps this story too is a little exaggerated, but at the Council of Florence John VIII Palaiologos, despite being Empereror of a much diminished Byzantine Empire on the verge of being overwhelmed by the Turks, conflicted with the Pope on all matters of rank. This was most apparent when he required workmen to make a hole in I believe the Pope's Palace in Florence, or Ferrara, to allow the Emperor to enter the hall without having to dismount to greet the Pope at his throne.
EDIT: It was Ferrara, not Florence. John would only proceed to the throne without his feet touching the ground, and he refused to be seen dismounting.
Found something similar in Ammianus book 30 reference 6, 3 (http://penelope.uchicago.edu/Thayer/E/Roman/Texts/Ammian/30*.html) where the Emperor Valentinian I dies in similar circumstances to what you have described while receiving envoys from the Quadi where they attempt to shift the blame for raids off their people and on to foreign bandits dwelling in their lands. Also I should mention Emperor Valentinian is not Byzantine but Roman reigning 364-375.