Trying to find the reference for the scientific experiment re: Toads and entombing, I've found this webpage article-
http://members.tripod.com/La_Mandragore/articles_toad.htm
It is somewhat remarkable that a 2003 article posted on Tripod is still accessible at its original URL today.
This article reviews the history of entombed animals claims, with reference to sources not often cited in the most commonly encountered reviews. The article moves on from stories about animals (particularly toads) entombed in stones to similar surprising animals discovered enclosed in (e.g.) cans of beans.
Here is the first portion of the article, which focused on the earlier stories of animals entombed in stone.
FROM THE ENTOMBED BUFO TO THE CANNED FROG :
IMPOSSIBLE FOSSILS AND CONTAMINATED FRENCH BEANS
By Jean Loïc LE QUELLEC
Widely distributed is the "Entombed Toad" motif, according to which toads could stay for months, years, centuries, millenia or even more, living without air, water or food, totally enclosed in compact blocks of marble, coal, concrete, sandstone or limestone, and crouching patiently until one day a hammer stroke liberates them. According to those stories, when a miner, a quarryman, a stone cutter or an archaeologist splits the lump, the batrachian blinks at the unaccustomed daylight, and hops placidly away. Sometimes, it can only survive but some hours or days after it is released .
The oldest case is quoted in a chronicle by Robert of Thorigny (1145). A living toad was found enclosed in a stone of the ramparts, at Le Mans : from the moment it was killed, its congeners began to pullulate along the town walls as never before . In 1198, William of Newburgh refers to a similar occurrence (Historia Anglia, Book 1, ch. 28). The allusions began to increase during the sixteenth century, as in the works of Simon Majol (Dies caniculares), G. Agricola (De Animalibus subterraneis), J. Cardan (De rerum veritate), U. Aldrovandus (De reliques animalibus exanguibus) and even Ambroise Paré, who relates how a large living toad was found in a big stone, in his vineyard of Meudon, before 1575 .
This belief is still alive ; connected with the medicinal properties attributed to that animal (which is supposed to suck the corrupted wind), it explains some observances in general use in the farms, and illustrated by the following narration of a young agriculturist, collected in 1989 :
"... that man used to put a toad in a flower pot, you know. He used to place it at a stable window, to cure a disease. I don't know what kind of disease it was (...) and... well, he told me that he forgot to remove the toad, and the toad stayed for goodness knows how long, may be one year, something like that, and it was as thin as a rake, you know... but it was still alive" .
An older variant of that apotropaic practice consisted in burying the toad in a flower pot under the stable threshold to protect the cattle. The occurrences mentioning such batrachians hermetically enclosed and subsisting on soil for years are a good many .
Living toads found in solid substances (rocks, trunk of trees) were periodically recorded by erudite scholars in the "Mémoires de l'Académie des Sciences" and in various scientific publications, during the seventeenth eighteenth centuries. Bob Skinner recently counted more that three hundred cases . During the nineteenth century, several scientists like A.M.C. Duméril , J.N. Vallot , or Frank and William Buckland , carried out very serious experiments to investigate that alleged phenomenon. For example, the last named, who was the first professor of Geology at Oxford University, prepared twenty four circular cells having a groove at their upper margin fitted to receive a plate of glass. Twelve were made of coarse oolithic limestone, and twelve were made in a block of compact siliceous sandstone. Dr Buckland took twenty four toads, both large and small, and placed one of each type in each of the above mentioned cells. "The large and small animals being distributed in equal proportion between the limestone and sandstone cells", before burying all the blocks under three feet of earth. Thirteen months later, the toads were examined. Every batrachian in the smaller cells was dead, "the greatest number of those in the large cells of porous limestone were alive", but there was some aperture in the cells, or cracks in the glass cover. Finally, all the animals died within two years, and the author came to the following conclusion :
"From the fatal result in the experiments (...), it seems to follow that Toads cannot live a year excluded totally from atmospheric air (...) ; it seems also probable that they cannot survive two years entirely excluded from food ; we may therefore conclude that there is a want of sufficiently minute and accurate observation in those so frequently recorded cases, where Toads are said to be found alive within blocks of stone and wood, in cavities that had no communication whatever with the external air (...). No examination is ever made until the reptile is first discovered by the breaking of the mass in which it was contained, and then it is too late to ascertain, without carefully replacing every fragment (and in no case that I have seen reported has this ever been done) whether or not there was any hole or crevice by which the animal may have entered the cavity from which it was extracted (...). The attention of the discoverer is always directed more to the Toad than to the minutiae of the state of the cavity in which it was contained."
By that statement, the scientific world learnt that toads are destined to die, and cannot survive eternally either in the stones found by miners or paleontologists or... in the canned French beans. Finally, the story told by the announcer of "Europe nû 1" demonstrates how some beliefs, corresponding to old world views, are harder to kill than any batrachian.
In 1856, a priest called Adolphe de Chesnel, in his famous "Dictionnaire des Superstitions", passed the following remarks about the latest entombed toad cases : "It is true that, in the present state of our knowledge, it is difficult to explain that irregular fact which is inconsistent with the laws laid down by the physical studies : but the Great Arbitrator of everything does not bind Himself to follow the professors'wanderings" .
Nevertheless, during the last century, a good many authors tried to solve rationally the problem of the "embedded reptiles", and it is interesting to consider their responses or explanations of the legend. For example, when the "Société Linnéenne de Paris" started in 1824 a competition around this difficult question, J.N. Vallot suggested that the term "crapaud" (toad) was used by the quarrymen and masons for a cavity in rock, and the expression "crapaud vivant" (living toad) for a geode lined with crystals. Illustrating the term "crapaud" (toad), Littré gives the meaning of : "coarse stone found in marble". For Bergen Evans, "The toad's clammy, corpselike feeling with its suggestion that it is already dead and hence no subject to mortality, may be the basis for many stories that one hears of a toad's being liberated from the centre of a block of stone or concrete in which he had obviously lived for years, or even centuries, without nourishment or air" .
More recently, M. Skinner proposed "an alternative explanation" : "There is a high rate of calcareous deposition in some limestone districts, as is demonstrated at the sites where objects suspended in dripping water become coated in a layer of stony deposition (...). A good proportion of entombed toad cases occurs in limestone areas, and this hypothesis may be valid in some of them although it has not been conclusively shown for how long such a toad could survive" . In 1985, the same author wrote that "The "toad in a hole", Sea serpent and giant Gooseberry were all classed together in the minds of some authors as the kind of stories now known as "Silly Season" tales. It is interesting to conjecture what their modern counterparts might be" .
It is noteworthy that the "entombed toads" are not regularly mentioned in the literature. Very rare in the mediaeval texts, they increased during the fifteenth sixteenth centuries, the highest rate being observed during the eighteenth and principally the nineteenth centuries. It's also during the last century that the studies, reports and experiments concerning the "impossible fossil" flourished. Later, the authors became more and more sceptic, humorous, and even frankly bantering. Obviously, it was no longer important to know if the story was true or not, for it was used by the journalists as an amusing way to fill in a space. For example, the "Glacial toad" or "Bufo compactilis" supposedly found near Frederick (Oklahoma) in "the same clay strata which has yielded relics of the Pleistocene or glacial age, of approximatively 300.000 years ago", was mentioned in the New York Times under date of April, 1rst, 1928.
For some decades, the "toad in the hole" has been ignored by the media. Since the quarrymen stopped working by hand, nobody cares about the toads well known by their predecessors (a "toad" being a real batrachian or some nodule or geode in a stone). Simultaneously, the development of geology and paleontology overthrew our Weltanschauung. Before the first third of the nineteenth century, it was still conceivable to find a living toad contemporaneous with the stone in which it was sleeping. On the one hand these animals could hibernate and fast for long periods ; on the other hand, the earth was supposed to be only created some thousand years ago. In the eighteenth century, the scholars calculated that the world was forty or sixty hundred years old, possibly seventy five according to the most audacious of them. It was only in the years 1860 1870 that a true notion of prehistoric men and civilizations was formed . As the chronologies grew longer and longer, the possibility for a toad to be entombed in a geological formation and to survive up to the present times appeared to be more and more incredible. Such a phenomenon is now as unlikely as the finding of a radio set in a solutrean layer. ...
FULL ESSAY:
https://members.tripod.com/La_Mandragore/articles_toad.htm
Anyway I can't find it on Snopes, and there are after all many accounts of it, not only within rock, but in cavities in trees. 
