I think this is confusing the journalism term "burying the lead" which can be spelled alternatively as lede and the word lede in the sense of leode, leod, or ledd which referred to the people tied to an allotment of land. You would be given land and lede, meaning the land and the labor of the people who lived there as your vassals. I've cut and pasted the OED entry below. But "Burying the lead/lede" starts showing up in the 1950s if you check it's etymology. Lede in the sense of the vassals and land is an Old English word dating to the 14th century.

Also, I've done a decent amount of reading on law of discovery and the development of property rights and surveying in the US, so this doesn't rule out anywhere else. I've also read a little on the Spanish. I've read a ton of old deeds from pioneer days in the US. I've never seen a buried lead marker and it doesn't really make sense. You want your claim to be visible to others so normally things were nailed to trees, scratched in rocks, or made somehow visible to others. You would do stuff like build a small fort to show that you've put labor into the area, even if you're not actually using it yet. But you wanted to create a visible sign of occupation and boundary to give other's notice.

And if you read old deeds, before a surveyor come come and mark everything off in terms of longitude, latitude, and chain length, they refer to visible landmarks. They'll say stuff like "Eastern boundary is X creek from from the creek branch, south 600 paces to the large oak tree. Southern boundary is from along X creek continuing to fence line of Sanders farm." The important thing again is that the boundaries are visible.

Not having it visible wouldn't help anyone show anything. The other problem is that the ground moves. Depending on where you buried something, how much water goes through the area, and the slope, where you bury stuff is going to move.

b. plural. In the alliterative phrase land and lede, i.e. land and vassals or subjects.

OE Andreas (1932) 1321 Hafast nu þe anum eall getihhad land ond leode.
c1330 Arth. & Merl. 86 And gaue him bothe land and lede To help his childer after his day.
1377 W. Langland Piers Plowman B. xv. 520 When Constantyn..holykirke dowed With londes and ledes lordeshipes and rentes.
?c1475 Sqr. lowe Degre 135 I wyll forsake both land and lede, And become an hermyte.
a1500 (▸?c1400) Sir Triamour (Cambr.) (1937) l. 1269 Y make the myn heyre Of londe and of lede.
a1500 Merchant & Son l. 7 in W. C. Hazlitt Remains Early Pop. Poetry Eng. (1864) I. 133 He was a grete tenement man, and ryche of londe and lede.