From Chapter 3:
Sometimes coltsfoot was mixed with tobacco. Ursula, the pig-woman and refreshment-booth keeper in Bartholomew Fair, in Ben Jonson's play of that name, says to her assistant: "Threepence a pipe-full I will have made, of all my whole half-pound of tobacco and a quarter of a pound of coltsfoot mixt with it too to eke it out."

From Chapter 8:
The allusion in these verses to a "satiric wipe" refers to a passage in the poem entitled "Conversation," which Cowper had written in the previous year, 1781. In this passage tobacco is abused in terms which Cowper clearly felt to need modification after his personal intercourse with such a smoker as his friend Bull. In describing, in "Conversation," the manner in which a story is sometimes told, the poet says:

The pipe, with solemn interposing puff,
Makes half a sentence at a time enough;
The dozing sages drop the drowsy strain,
Then pause and puff—and speak, and pause again.
Such often, like the tube they so admire,
Important triflers! have more smoke than fire.