The term "Shaivite" is overused nowadays. For instance, Iyer Brahmins are often called Shaivites, but they're actually followers of Adi Shankaracharya's Smartha sect (which I discuss here and here), and simply adopt Shiva as their Ishta Devata. True philosophical Shaivism is relatively rare nowadays (in contrast to philosophical Vaishnavism which is pretty common). I discussed one genuine Shaivite sect, the Lingayat sect of Basava, in my answer here. But my question is related to a more famous sect of Shaivism, known as Shaiva Siddhanta, which is based on the Shaiva Agamas and the poems of the Nayanars just as the Sri Vaishnava sect (of which I'm a member) is based on the Pancharatra Agamas and the poems of the Alwars.
In any case, one of the defining works of the Shaiva Siddhanta sect is Meykandar's Shiva Jnana Bodham, a commentary on twelve important verses from a Shaiva Agama called the Raurava Agamas. Now Meykandar's shishya Arulnandi Shivacharya wrote a work called the Shivajnana Siddhiyar, which is a commentary on Meykandar's work but also tries to refute rival schools of philosophy. In this excerpt from the Shiva Jnana Siddhiyar, Arulnandi Sivacharya refutes Buddhist philosophy by showing that all Buddhist theories of how physical bodies originate are incorrect:
If you say bodies are formed from the mixture of four elements, then these cannot unite as their natures are opposed to each other. If you say they are formed by the union of blood and semen, then account for toads being found in the heart of rocks, and worms in the heart of trees. If you say the real cause is good and bad Karma, then these, being opposed, cannot join and form bodies. If food is the cause, then the food which in youth develops the body is not capable of preventing decay in old age. If intelligence is the cause, then that which is formless Chaitanya cannot assume Achaitanya (non-intelligent) form. If you assert that bodies are formed from nothing, then we could cull flowers from the sky.
I'm interested in the part in bold. Arulnandi Shivacharya is saying that intercourse cannot be the ultimate cause of the creation of bodies, because there are toads that are found in the center of solid rocks, and those toads couldn't have been produced through intercourse since there would be no way for the parents to get inside the rocks in the first place.
He states this fact as if it's common knowledge, but it's not common knowledge to me! So my question is, are there any scriptures which describe toads being found in the heart of rocks? And how exactly are toads found in the heart of rocks born if it not by intercourse? Are they magically created somehow?
On a side note, I found a journal paper written in 1834 about claims of toads being found in solid rocks. Still, along with Adi Shankaracharya's claim described in my question here, Arulnandi Shivacharya's claim suggests to me that the experiences of ancient Indians were very different from our own.