My copy of Book 2 claims this was devised by the Earl of Dunmore, but later sources seem unsure. The The Thistle has an article on its origins.

The RSCDS numbers couples clockwise (while modern square dance numbers them counter clockwise).

Arthur Miller, Leeds, 1900 writes:

1. All join hands in circle, and turn round to places.
2. Gentlemen take hold of partner's hand, and ladies give hands across and round, gentlemen give left hands across and back to places.
3. All set and turn partners.
4. Grand chain

RSCDS Book 6 claims this was "collected in Oxton, Berwickshire."

Clearly based on The Eightsome Reel just as in quadrilles where The Lancers for 16 was based on The Lancers.

In his A Companion to the Ball Room, 1816, Thomas Wilson published Lady Mary Douglas:, wherein he writes:

SINGLE FIGURE Tune played straight thro and Da Capo
Whole figure at top   lead down the middle up again turn your partner   & lead outsides  

OR THUS Cross over 2 Cu:   cross up 1 Cu: towards the top and half figure round the top Cu:   & the double triangle  

DOUBLE FIGURE Tune played twice thro and Da Capo
Hey on your own sides   chain figure 6 round   lead down the middle up again lead thro the top Cu:   whole figure round the bottom Cu:   turn corners   whole figure contrary corners  

The music consists of 2 eight bar strains. The RSCDS has chosen the DOUBLE FIGURE which means the music should be played ABBABB (I think). " " indicates a strain.

Wilson defines his figures in his An Analysis of Country Dancing.

• Hey on your own sides is only defined as part of "Hey Contrary Sides, and Hey of your own Sides" on page 83 and he shows a mirror/reflection hey.
• Chain figure of six may be found on page 78 of the 3rd edition of the Analysis (1811). The top couple face their partner, as the others face their neighbor then everyone does rights and lefts until they return to where they started. Wilson does not specify how to fit the 6 changes into 8 bars of music.
• lead down the middle up again may be found on pages 10-11 and means: "lead down two couples, turn, lead up to the place of the couple who were below (who move up)" Wilson does not specify a hand hold for the lead, nor whether the 2s take hands.
• lead thro the top Cu: is half of through bottom and top on page 23 and means "the active couple take hands, lead above the top, drop hands, and cast up to their own places.
• whole figure round the bottom Cu: is defined as whole figure at top (that is when the 1s are at top so they figure through the couple below them) may be found on pages 12-13 and means "the active lady starts and crosses down, looping around the man below her then she again cross between the couple below, looping around the woman below and casts up to her own place. The active man starts a little after her and mirrors her motions, looping the woman below and then the man below."
• turn corners may be found on pages 28-32 and appears to mean: the 1s pass partner right shoulder to turn first corners with both hands, then pass each other right shoulder to turn second corners (presumably again with both hands, though Wilson does not specify), finally passing each other left to return to places.
• whole figure contrary corners is found on page 104 of the 3rd edition of the Analysis (1811). Rather awkwardly, Wilson provides two different (contradictory) directions. In the first "the 1s cross down, W1 in front of M1, W1 around M3, M1 around W3, then cross up, W1 around W2, M1 around M2, and return home". In the second the "1s cross up, W1 around M2, M1 around W2, then cross down W1 around W3, M1 around M3, and return home.

The crib diagram attributes to Wilson, 1825. According to The Regency Dance site Wilson didn't publish anything in 1825. The Scottish Country Dance Database also gives a date of publication as 1825, but gives no devisor.

Quite a number of people published dances named I'll gang nae mair to yon town but none matches the RSCDS figure: Thomas Wilson, 1809, Hime, 1810, Chivers, 1821, Chivers, 1821 (different work), J.P. Boulogne, 1827, R. Hill, 1830.

The crib diagram attributes this to the Blantyre MS which is dated ~1805. I cannot verify this claim.

A dance with this name was published by Button & Whittaker, but whether it matches the figure I do not know. The RSCDS attributes this dance to the publishers but Wilson was the deviser: see the Regency Dance site's paper on Button and Co. The use of double triangles does suggest Wilson was the choreographer.

SINGLE FIGURE 1^st. strain played straight thro 2^d. repeated
Hey on your own sides  
swing with right hands round 2^d. Cu: then with left
OR THUS Cross over one Cu: half figure round the 3^d. Cu:   & lead outsides  

DOUBLE FIGURE Tune played twice thro as marked
Whole figure at top   Chain figure 6 round   lead down the middle up again & right & left with top Cu:   & lead through the bottom & top  

The music is an eight bar strain and a four bar strain. In the double figure (which is what the RSCDS uses) these should be played ABBABB.

Wilson defines most of his figures in his An Analysis of Country Dancing, 3rd Edition.

1. Whole figure at the top may be found on page 39. The active lady starts and crosses down, looping around the man below her then she again cross between the couple below, looping around the woman below and casts up to her own place. The active man starts a little after her and mirrors her motions, looping the woman below and then the man below.
2. Chain figure of six may be found on page 78. The top couple face their partner, as the others face their neighbor then everyone does rights and lefts until they return to where they started. Wilson does not specify how to fit the 6 changes into 8 bars of music.
3. Lead down the middle, up again may be found on page 7. The top couple meet and join hands, then lead down to between the 3s, and lead back to 2nd place as the 2s move up. This usually takes 4 bars.
4. right and left may be found on page 46-49. It does not mean what I expect, instead: 2nd corners change by left shoulders, 1st corners right, 2nd corners change back by left, 1st corners by right. And all of this in four bars
5. Wilson does not seem to define lead through the bottom & top but it seems self-explanatory.

RSCDS Book 18 says "collected in Aberdeenshire (Hill MS - adapted)."

Book 21 has a note: "Collected in Aberdeenshire."

The RSCDS gives no source to this dance, but it appears to be derived from Nathaniel Kynaston's Mrs. Hill's Dance published by both Walsh and Playford in 1710.

Note: Each Strain is to be play'd twice over.

The first Cu. slip down the middle, and Sett a-cross to the third Cu. then first Man turn the third Wo. and the first Wo. turn the third Man Then Sett a-cross to the 2d Cu. then first Man turn the 2d Man half round, and the first Wo. turn the 2d Wo. at the same Time Then Right-hand and Left round, then turn Partners Proper Then the Man slips between the 2d Cu. and cast off, the first Wo. at the same Time go between the third Cu. and cast up, then both turn in the 2d Couple's Place

John Young calls the dance Pretty Poll and writes:

Note: The first Strain is to be play'd twice, and the second once, and so far as the Repeat again.

The first Couple cast off and turn Hands This to the first Strain play'd once The second Couple do the same This to the first Strain play'd twice Then the first Couple clap Hands and cast off below the second Couple, then all four change Places, and Right and Left half round and cast off This to the second Strain play'd once Then clap Hands and turn single This from the Repeat.

The original music is in 3/2 time and consists of a 5 bar strain and an 8 bar strain, intended to be played AABA.

Goulding spells the title The Land of Cakes.

The adaptation is rather loose.

SINGLE FIGURE (Each strain repeated)
Hands 3 round on the ladies side hands 3 round on the gent^ns. side   lead down the middle up again & allemande  

OR THUS Set & change places with 2^d. Cu: set & back again   & whole poussette  

DOUBLE FIGURE (Tune played twice thro' with repeats)
Set & hands across quite round with 2^d. Cu: set & back again   lead down the middle up again set to top Cu:   swing corners   chain figure four round with top Cu: & turn your partner  

The music consists of two 4 bar strains. Probably played as a reel rather than a strathspey.

The RSCDS is interpretting Wilson's DOUBLE FIGURE

Wilson defines most of his figures in his An Analysis of Country Dancing, 3rd Edition.

1. Set & hands across quite round is one figure which Wilson does not define. However he defines hands across on page 12 where he defines a normal hands across but says they only turn half round (with a footnote saying it is often done by turning completely round and then back again).
   So I'm going to assume that quite round actually means half round. So two bars of setting, followed by two bars to do half a hands across.
2. lead down the middle up again set to the top Cu: may be found on page 8 Top couple leads down to between the third couple, 1s turn and lead up to 2nd place as the second couple move up (Wilson's pictures show them moving up the sidelines and not leading), then actives set (or foot it) to the second couple. (This seems to take 8 bars)
3. swing corners is defined on pages 55-58 and appears to mean: the 1s turn partner by the right hand then 1st corners by the left hand, partner right, 2nd corners left and returning home the shortest way (by the left shoulder).
4. Chain figure for four may be found on page 76 and boils down to what anyone else would call rights and lefts.
5. Turn your partner may be found on page 2 and boils a two hand turn (Wilson calls a right hand turn "swing your partner").

In 1796 Longman & Broderip published a dance called "The Marquis of Lorn's Strathspey", and in ~1799 (in his 14th book) William Campbell published a different figure with the same name. Neither one matches this dance.