Here's a scrap I came across and found in my notebook. I'll have to go back and trace its source again. In the meantime, can you solve it?
I found a four-voice solution. As each part repeats, it does so at a lower pitch, as suggested by the epigram: "SOL POST VESPERAS DECLINAT:" "After the evening the sun sets." Of course the 'declinat' has a double meaning.
You'll want to choose the intervals of the entries so that consonances are formed on beats. These being unisons, thirds, fifths, sixths and octaves, and so on. But you will find a few lovely dissonances resolving to these. Good luck adjusting the accidentals as the canon descends. I stopped on E-flat.
I've transcribed it here in the original tenor clef and also in bass clef.
See "The Solution to Sol post vesperas declinat"