SOURCE: A Grammar of the Latin Language, by D. Yenni (1845) at GoogleBooks. This is just a little joke, not a fable - but it seemed to fit the spirit of Aesop very nicely!
READ OUT LOUD. Choose which marked text you prefer to practice with - macrons or accent marks - and read the text out loud until you feel comfortable and confident. Then, try reading the unmarked text at the bottom. It should be easy for you after practicing with the marked texts. :-)
MACRONS. Here is the text with macrons:
Quīdam flūmen trāiectūrus, equō īnsidēns nāvem cōnscendit. Cum quis causam percontarētur: Festīnō, inquit.
ACCENT MARKS. Here is the text with ecclesiastical accents, plus some color-coding for the words of three or more syllables (blue: penultimate stress; red: antepenultimate stress):
Quidam flumen traiectúrus, equo ínsidens navem conscéndit. Cum quis causam percontarétur: Festíno, inquit.
UNMARKED TEXT. Here is the unmarked text - after practicing with the marked text that you prefer, you should not have any trouble with the unmarked text:
IMAGE. Here is an illustration for the story (image source) showing some horses on board a ship of sorts!