Rabbi Akiva taught that there were three things Moses could not visualize on his own, no matter how great his prophetic power. God had to physically point them out to him.
The first was the new moon. When God instructed Moses about the lunar calendar, Moses could not picture exactly what phase of the moon marked the beginning of a new month. God had to show him directly. The second was the identification of impure swarming creatures. (Leviticus 11:29) says, "And this shall be unclean for you from among all the things that swarm upon the earth" — the word "this" implying that God pointed to each creature and said, "This one." The third was the construction of the menorah. (Numbers 8:4) states, "And this is the work of the menorah," again using the demonstrative "this," indicating that God had to show Moses a model because the design was too complex to convey through words alone.
Other sages added a fourth item to the list: the laws of slaughtering sacrificial animals. (Numbers 29:38) says, "And this is what you shall do upon the altar," suggesting that the precise method of slaughter also required divine demonstration.
This teaching is remarkable for what it reveals about the rabbinic view of Moses. Even the greatest prophet who ever lived — the man who spoke with God face to face — had limits to his comprehension. Some sacred things cannot be transmitted through language. They must be seen. The Mekhilta quietly insists that even Moses needed God to show, not just tell.