What does “l. s. d.” stand for?

Here is the original text from Lord Macaulay’s History of England:

They are the men of double entry, magnifying routine. In business they have added mechanical device to mechanical device, they have put wind, water, steam, and electricity into subjection; they have done most of the reckoning in England, and their brains are hieroglyphed with l. s. d.

Source: Macaulay, Thomas Babington. The History of England from the Accession of James the Second. Boston and New York: Houghton, Mifflin and Company, 1901. xviii. Print.

Solution 1:

Given the location and the period, I think it's likely to be a commonly-used variant of "£sd" for "pounds, shillings, and pence" - that is, money. The abbreviation comes from the Latin librae, solidi, denarii.

Solution 2:

L.S.D. was the standard abbreviation for "Pounds, shillings, and pence". See wikipedia.

Note that wikipedia claims it was usually written £sd and "sometimes" as Lsd. That was not my experience - I would have said "l. s. d." was at least as common. (Source: I was 13 when the UK decimalized).