"The worth of a cat that is killed or stolen. Its head is to be put downward upon a clean even floor, with its tail lifted upwards, and thus suspended, whilst wheat is poured about it until the tip of its tail be covered, and that is to be its worth."
There's more detail to that cat valuation in later versions of the code, such as this pungent note:
In "The Gwentian Code," chap. XX., the value of a cat is increased since the former edicts. After relating the mode of calculating the value of the king's cat, by holding it by the tail and covering it with wheat, it says, as to the cat's qualities:
"3rd. That it be perfect of ear, perfect of eye, perfect of teeth, perfect of tail, perfect of claw, and without marks of fire."
If a cat was found faulty in any one of those particulars, a third of her price was to be refunded to the purchaser. There were two reasons for the condition with respect to fire, for cats which lie much by the fire side are generally lazy and bad mousers, and also if they have been singed at all the rats would be sure to discover them by the smell.
This is found on pages 33-4 of (honest, the whole book title) The Model Merchant of the Middle Ages: Exemplified in the Story of Whittington and His Cat: Being an Attempt to Rescue that Interesting Story from the Region of Fable, and to Place it in Its Proper Position in the Legitimate History of this Country, by Samuel Lysons (Hamilton, Adams, 1860).