From Chapter 3:
The fumes of dried coltsfoot leaves were used as a remedy in cases of difficulty of breathing, both in ancient Roman times and in Tudor England. Lyte, in his translation, 1578, of Dodoens' "Historie of Plants," says of coltsfoot: "The parfume of the dryed leaves layde upon quicke coles, taken into the mouth through the pipe of a funnell, or tunnell, helpeth suche as are troubled with the shortnesse of winde, and fetche their breath thicke or often, and do [sic] breake without daunger the impostems of the breast." The leaves of coltsfoot and of other plants have often been used as a substitute for tobacco in modern days. A correspondent of Notes and Queries, in 1897, said that when he was a boy he knew an old Calvinist minister, who used to smoke a dried mixture of the leaves of horehound, yarrow and "foal's foot" intermingled with a small quantity of tobacco. He said it was a very good substitute for the genuine article. Similar mixtures, or the leaves of coltsfoot alone, have often been smoked in bygone days by folk who could not afford to smoke tobacco only.

From Chapter 5:
When plague was abroad even children were compelled to smoke. At the time of the dreadful visitation of 1665 all the boys at Eton were obliged to smoke in school every morning. One of these juvenile smokers, a certain Tom Rogers, years afterwards declared to Hearne, the Oxford antiquary, that he never was whipped so much in his life as he was one morning for not smoking. Times have changed at Eton since this anti-tobacconist martyr received his whipping. It is sometimes stated that at this time smoking was generally practised in schools, and that at a stated hour each morning lessons were laid aside, and masters and scholars alike produced their pipes and proceeded to smoke tobacco. But I know of no authority for this wider statement; it seems to have grown out of Hearne's record of the practice at Eton.