The Roman Credit Crisis
Rome enforced an old law requiring senators to hold a share of their wealth in Italian land, and gave them eighteen months to comply. Everyone called in their loans at once to buy property; borrowers dumped assets to repay; land prices collapsed as the forced buying was swamped by forced selling. Credit froze. Tiberius ended it by putting 100 million sesterces of treasury money into banks to lend interest-free for three years, against land as security. A regulatory deadline triggered a liquidity crisis, and the state stopped it with an emergency injection into the banking system — in the reign of Tiberius.
A speculative belief detaches asset prices from fundamentals; the belief breaks and prices collapse.