Definition:Quaternion/Historical Note

Historical Note on Quaternions
The quaternions were famously conceived by, who was so proud of his flash of insight that he carved:
 * $i^2 = j^2 = k^2 = i j k = -1$

into the stone of Brougham Bridge on $16$th October $1843$.

However, it is also worth noting that independently came up with the same concept in $1819$.