I am just going to leave this as a short list, because it is quite awesome. I only wish he had written a little more about such things — though perhaps he did, I am discovering there are larger collections about than the old  old and free version I got off Gutenberg:

18 June, 1768

I need not remind a gentleman of your extensive reading of the excellent account there is from Mr. Derham, in Ray’s Wisdom of God in the Creation (p. 365), concerning the migration of frogs from their breeding ponds. In this account he at once subverts that foolish opinion of their dropping from the clouds in rain…

27 July, 1768

In my visit I was not very far from Hungerford, and did not forget to make some inquiries concerning the wonderful method of curing cancers by means of toads.

On the village of Tring in Hertfordshire — I quite want to visit:

8 Jan 1776

In a farm-yard near the middle of this village stands, at this day, a row of pollard-ashes, which, by the seams and long cicatrices down their sides, manifestly show that, in former times, they have been cleft asunder. These trees, when young and flexible, were severed and held open by wedges, while ruptured children, stripped naked, were pushed through the apertures, under a persuasion that, by such a process, the poor babes would be cured of their infirmity. As soon as the operation was over, the tree, in the suffering part, was plastered with loam, and carefully swathed up. If the parts coalesced and soldered together, as usually fell out, where the feat was performed with any adroitness at all, the party was cured; but, where the cleft continued to gape, the operation, it was supposed, would prove ineffectual. Having occasion to enlarge my garden not long since, I cut down two or three such trees, one of which did not grow together.

We have several persons now living in the village, who, in their childhood, were supposed to be healed by this superstitious ceremony, derived down perhaps from our Saxon ancestors, who practiced it before their conversion to Christianity.

On leprosy:

8 Jan 1778

The good women, who love to account for every defect in children by the doctrine of longing, said that his mother felt a violent propensity for oysters, which she was unable to gratify; and that the black rough scurf on his hands and feet were the shells of that fish. We knew his parents, neither of which were lepers; his father in particular lived to be far advanced in years.

(Gilbert White on matters more natural historyish from the bulk of his letter here, and on community resistance to enclosing the commons here)