What is the meaning of this Voltaire quote ?
Nos cinq sens imparfaits, donnés par la nature, de nos biens, de nos maux sont la seuls mesure.
I can't even parse this sentence.
It's a hard one to parse because it's part of a poem. The syntax has been distorted to produce the rhyme.
In a nutshell: "the five senses nature gave us, though imperfect, are the only way we can judge (measure) what is good or bad to us"
Here good and bad are not to be taken in the moral sense, but as adequate to our well being. As in "poverty is bad" and "wealth is good".
I took a look at the context, it seems to be part of the first discourse in Discours en Vers sur l'Homme, where Voltaire tries to argue that, beyond appearances, all people are equal in condition.
Right before OP's quote he states "Les mortels sont egaux, leur masque est différent" -> "mortals are equal, their masks (appearances) are different", and right after argues that even kings don't have more than 5 senses.
I claim no familiarity with this particular work, but from a rapid reading it looks like a very typical Voltaire-ish argument that rich people and kings also have their problems, and therefore poor people should not envy their condition or question why they are poor too much. Providing arguments as to why poor people should stay in their place is something Voltaire did a lot and it made him quite popular among the rich and opulent.