“A Scots pint”
What it means
Considerably more drink than an English visitor expects.
Where it comes from
The Scots pint held about 1.7 litres, close to three imperial pints, and its standard was the Stirling Jug held by that burgh. Ordering one on the wrong side of the border produced very different results.
How sure are we?
The unit is genuine and its abolition at the Union in 1707 is documented, but the measure survived in speech long afterwards. Burns writes of pints in a sense no English reader pictures correctly.