Preserve a sort of mystery as to yourself.

There is no reason why you should not speak, but even then guardedly, of the wonders of the land inhabited by white men many months' sail across the seas; but it were best that as little should be said as possible.
"Montezuma is sure to wish to see you, but before you visit him, we will again take counsel together." "I will, to the best of my power, carry out your Majesty's orders," Roger said.

"I fully recognize their wisdom.

Indeed, neither at Tabasco nor upon the journey, either to the merchants or to your envoys, have I said a word respecting the Spaniards; but I thought that it was but right that you should know the truth of the matter, especially when you told me of the prediction of your royal father.
In future, when I am asked questions, I can always fall back upon silence and reply, truly, 'I am forbidden to tell this.'" "That will do excellently," the king said.

"There is but one point connected with you now that puzzles us--a point which, before you came, confirmed us in the belief that there was something supernatural in your character: How is it that you have come to understand and speak our tongue ?" Roger smiled.
"To anyone else, your Majesty, I should have replied, 'I am forbidden to answer that question;' but I wish not to have any mystery with you.