I was trying to read the original 木兰辞 poem. But I found two versions of it on the internet.
One line reads:
In the other version it's:
Which one is the original one?
Both are correct, you might have noticed in many ancient poems, some characters or even an entire sentence could have different versions, which are both or all correct. Some readers may favour one version while other may favour another.
There are many reasons for this to happen. First, in ancient times, there is no easy way of copying and pasting, reproduction is thus relayed on people if you do not happen to have the original printing template, which could introduce flaws. Moreover, the author could have made adjustment to his or her work many times, therefore different versions could be in circulating contemporarily.
There could be many other reasons, please see this post.
By the way, in case if you are curious, please refer to this webpage for the meaning of 明驼。
Mulan returned to see the emperor. The Emperor asked what she wanted for reward. Mulan told the Emperor she didn't want anything, just wish to borrow a fast horse (we can presume the Royal court had the best horses) so that she could ride it and get home faster to see her family.
Mulan was pretending to be a man, by refusing the reward from the emperor, she put herself in a better position in case she was discovered and need to beg for forgiveness.
To not appear rejecting the emperor's good will, she asked for a simple item with virtuous reason- She was a good 'son' trying to serve 'his' elderly father again as soon as possible
If you say "愿(驰)千里足" - "wish to (ride) a fast horse that can run thousand miles" Then you have to presume she had such a horse or a way to get such horse elsewhere. It didn't answer to the Emperor's question of "what you want for reward"
"願(借)明駝千里足" is more logical, therefore, I support it as the original version. Even if it was not the original, I still support it as the 'standard' version today