Which line in the poem London, 1802 by William Wordsworth uses metonymy to refer to art and literature?

In the poem "London" (1802) written by William Wordsworth the use of metonymy to refer to art and literature has been done in the third line of the poem.

"Of stagnant waters: altar, sword, and pen,"

The use of the word "pen" by Wordsworth doesn't mean any great or powerful or huge writing instrument rather he is referring to the English literary tradition of the past.

Metonymy is a figure of speech which uses an attribute or any associated word with the thing it is related to or it is a part of.