Mandates for impossible objects were squashed just after .40d, or there about.
These days, nobles make "Demands", but those can be safely ignored. In the past, you could be faced with the following problem:
1) A noble that you did not select shows up to your fortress.
2) They refuse to work. AT ALL.
3) They make recurring demands for slade beds and native aluminum axes. (No, literally.)
4) They end up killing or otherwise disabling (through repeated imprisonment) your highly skilled workforce, because of these dumbass mandates that cannot possibly be met.
This is why "Unfortunate accidents" were REAALY popular back then, and why people that didnt want to commit repeated regicide would outfit the hammerer with a styrofoam candy mallet instead of an actual hammer instead. "50 lashes with a wet noodle" kind of punishment gets the obstruction overwith quickly, and mostly painlessly.
Unless somebody hoards images for years and years, you wont get many good pics of absurd mandates, unless somebody is a masochist and is playing 40d.