"[arriving in the first age, regardless of which] Much to learn. First, the stone Slate. Pick it up from the pedestal and take it with you But know this about the Slates: They too are abominations, made by the Bahro creatures' abuse of the Art of Writing. Still... they carry great power. You will find that you can write on the Slates, anything you wish. There are some elementary symbols the creatures understand. At least in this way, you can use the Bahro hindrance for your good. They will take it, if you drop it. They will obey it, if you order them. They will return it, in time. As you learn, you will have more control."
January 1, 1970
https://en.wikiquote.org/wiki/Myst_V%3A_End_of_Ages