Alexander Pope

Isaac Thompson, in "An Essay on Poetry" Thompson, Collection of Poems (1731) 150-51.

Hence the best Poets first the Muse assail,
In rural Shades, and easy Pastoral;
But gath'ring Strength, by just Degrees arise,
And with the Lark, exchange the Plains for Skies.

Immortal MARO thus begins with Swains,
In TITYRUS' and MELIBAEUS' strains;
First his young Muse appears a Silvan Maid,
And sings two Shepherds in a beechen Shade;
But leaving these, she rides thro' Storms and Floods,
With Heroes fights, and thunders with the Gods.
And thus, a Bard, in later Times inspir'd,
(To Windsor's blissful Plains and Shades retir'd;)
On Thames' delightful Banks, his Numbers try'd,
Now DAPHNIS spoke, and STREPHON then reply'd:
But soon in higher Flights his Muse was known,
And all the mighty Iliad was his own:
For him, had Fate th' Odyssey kept so long,
For him ULYSSES rang'd, and HOMER sung.
Let this be then your unambitious Aim,
First to make Woods, and Hills, and Springs, your Theme:
From wild Conceits these Subjects are most free,
And teach you best, the old Simplicity;
There, learn to flow in Verse, from ev'ry Stream,
And Plains, draw sweet variety from them,
Vales will teach lowliness, and Mountains, heigh;
Those to depress, and these to raise your Flight;
What's soft and mild, kind Breezes will inform;
And what is fierce and rough, the raging Storm.