I once had my own superconductor. It was a metal bar at 4 degrees K. I ran a current through it of 100 amperes and tried to find the voltage across it. I had a very sensitive nanovoltmeter. It could see 10 nanovolts if they were there. I could not detect anything.
One time I saw a magnet levitating piece of liquid nitrogen temperature superconductor. This is the "new" stuff .
Levitation that works:
Just cool a frying pan made of lead down to 2 degrees K and put a strong
bar magnet on it. The bar
magnet will see a mirror image of itself in the lead sheet and be repelled
hence levitated. It can be
moved about effortlessly.