<div>
    <style scoped>

        .button-xsmall {
            font-size: 70%;
        }

        .button-small {
            font-size: 85%;
        }

        .button-large {
            font-size: 110%;
        }

        .button-xlarge {
            font-size: 125%;
        }

    </style>

    <button class="button-xsmall pure-button">Extra Small Button</button>
    <button class="button-small pure-button">Small Button</button>
    <button class="pure-button pure-button">Regular Button</button>
    <button class="button-large pure-button">Large Button</button>
    <button class="button-xlarge pure-button">Extra Large Button</button>
</div>

<div>
    <style scoped>

        .button-xsmall {
            font-size: 70%;
        }

        .button-small {
            font-size: 85%;
        }

        .button-large {
            font-size: 110%;
        }

        .button-xlarge {
            font-size: 125%;
        }

    </style>

    <button class="button-xsmall pure-button">Extra Small Button</button>
    <button class="button-small pure-button">Small Button</button>
    <button class="pure-button">Regular Button</button>
    <button class="button-large pure-button">Large Button</button>
    <button class="button-xlarge pure-button">Extra Large Button</button>
</div>

Remove duplicate class in button documentation
Remove duplicate class in button documentation

The pure-button class is applied twice on a regular button in the
sizes.handlebars partial.
