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:
Leō, aestū cursūque dēfessus, in umbrā quiescēbat. Mūrium autem grege tergum eius percurrente, expergēfactus ūnum ē multīs comprehendit. Supplicat misellus, clāmitāns indignum sē esse cui īrascatur. Leō, reputāns nihil laudis esse in nece tantillae bestiolae, captīvum dīmittit. Nōn multō post, Leō, dum per segetēs currit, incidit in plagās; rūgīre licet, exīre nōn licet. Rūgientem Leōnem Mūs audit, vōcem agnoscit, rēpit in cunīculōs, et quaesītōs laqueōrum nōdōs invenit corrōditque. Quō factō, Leō ē plagīs ēvādit.
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):
Leo, aestu cursúque deféssus, in umbra quiescébat. Múrium autem grege tergum eius percurrénte, expergefáctus unum e multis comprehéndit. Súpplicat miséllus, clámitans indígnum se esse cui irascátur. Leo, réputans nihil laudis esse in nece tantíllae bestíolae, captívum dimíttit. Non multo post, Leo, dum per ségetes currit, íncidit in plagas; rugíre licet, exíre non licet. Rugiéntem Leónem Mus audit, vocem agnóscit, repit in cunículos, et quaesítos laqueórum nodos ínvenit corrodítque. Quo facto, Leo e plagis evádit.
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:
Leo, aestu cursuque defessus, in umbra quiescebat. Murium autem grege tergum eius percurrente, expergefactus unum e multis comprehendit. Supplicat misellus, clamitans indignum se esse cui irascatur. Leo, reputans nihil laudis esse in nece tantillae bestiolae, captivum dimittit. Non multo post, Leo, dum per segetes currit, incidit in plagas; rugire licet, exire non licet. Rugientem Leonem Mus audit, vocem agnoscit, repit in cuniculos, et quaesitos laqueorum nodos invenit corroditque. Quo facto, Leo e plagis evadit.
IMAGE. Here is an illustration for the story (image source).