"Limitation on preaching with the admonition to refrain from all vicious attacks, fairy tales, and controversies that delight in the abuse of others, and to present instead a short and apt oration. (Prince-bishop of Mainz to the heads of the orders, in particular the Capuchins, Nov. 1789)" (1)
This was mentioned as part of a series of edicts designed to keep sermons from becoming entirely too long, so that "listeners are not inundated, pregant women not discomfited, the poorly dressed do not freeze, and the poor can prepare their meals". (2) One certain sign of a preacher going on too long is if they "speak at length in unknown languages, Greek, Hebrew, and the like". While you're at it, avoid "unnecessary repetitions and so-called tautologies." (4) This is as good advice now for teaching a class or conducting a meeting as it was then for preaching.
(1) Quote quoted from Gerhard Dohrn-van Rossum, History of the Hour. (Chicago: The University of Chicago Press, 1996). p. 265.
(2) (Thorn, 1560-1570) Dohrn-van Rossum, 264.
(3) (Electorate of Saxony 1671) Dohrn-van Rossum, 265.
(4) (Brandenburg-Prussia 1714) Dohrn-van Rossum, 265.