A plaque on Broom Bridge in Dublin, commemorating Hamilton's invention of w:quaternions
The plaque says:
Here as he walked by
on the 16th of October 1843
Sir William Rowan Hamilton
in a flash of genius discovered
the fundamental formula for
quaternion multiplication
i2 = j2 = k2 = i j k = −1
& cut it on a stone of this bridge
My father took the picture and agrees to transfer the copyright to me.