Princes like to be helped, but not surpassed. When you counsel someone, you should appear to be reminding him of something he had forgotten, not of the light he was unable to see.

[Gustan de ser ayudados los príncipes, pero no excedidos, y que el aviso haga antes viso de recuerdo de lo que olvidaba que de luz de lo que no alcanzó.]

Baltasar Gracián y Morales (1601-1658) Spanish Jesuit priest, writer, philosopher

The Art of Worldly Wisdom [Oráculo Manual y Arte de Prudencia], § 7 (1647) [tr. Maurer (1992)]
    (Source)

(Source (Spanish)). Alternate translations:

Princes are willing to be assisted, but not surpassed. Those who advise them ought to speak as if they put them in mind of what they forgot, and not as teaching them what they knew not.
[Flesher ed. (1685)]

They [princes] will allow a man to help them but not to surpass them, and will have any advice tendered them appear like a recollection of something they have forgotten rather than as a guide to something they cannot find.
[tr. Jacobs (1892)]

They [kings] may abide being helped, but not surpassed, wherefore let advice given them appear more a jog to what they forgot, than a light to what they could not find.
[tr. Fischer (1937)]