Why did the seventeenth century French hide their "rentes sur l'Hôtel de Ville de Paris" from the Crown? This article describes the behaviour of modern-era rentiers (the so-called 'coupon clippers') who evaded every attempted tax assessment on their securities. These attempts resulted in capital losses; the higher the nominal debt, the higher the loss. However, it must then be accounted, beyond the intrinsic difficulty of assessment, what was the advantage to hide the assets from market exchange and repayment by the state. A comparison with current accounting standards and their interpretation by investment banks during the last financial crisis is illuminating: the unintelligible behaviour of old-fashioned coupon clippers seems to be parallel to the most rational and calculating practice of contemporaneous finance.